OPINION
Opinion by
Lindsay Tope and Milton D. Tope appeal the trial court’s granting of Brazoria County Children Protective Services’ (CPS) motion to dismiss their petition for adoption based on lack of standing.1 The Topes are the maternal grandparents of the children they are seeking to adopt. When Melissa Cole, Lindsay Tope’s daughter, and her husband had their parental rights terminated on or about November 29, 2004,2 the children were placed with their paternal aunt. On January 27, 2005, the Topes filed a petition to adopt their grandchildren. On February 17, 2005, CPS filed a “motion to dismiss” alleging the Topes lack standing to file an original petition for adoption. Seven days later, on February 24, 2005, the trial court held a hearing on CPS’ motion and dismissed the petition.
The Topes complain that the trial court erred in three respects in dismissing the suit: 1) because there was no procedural basis to dismiss the Topes’ case, 2) the out-of-state grandparents had “substantial past contact” with the children, and 3) without allowing the Topes to discover evidence concerning CPS’ refusal to consent to the adoption. Because standing can be challenged through procedural means other than summary judgment and the Topes did not have substantial past contact as a matter of law, we affirm the judgment of the trial court.
Standing Can Be Challenged By Means Other Than Summary Judgment
In their first point of error, the Topes argue the trial court erred proee-*869durally in dismissing the case. Standing, as a necessary component of a court’s subject-matter jurisdiction, is a constitutional prerequisite to maintaining a suit under Texas law. Tex. Ass’n of Bus. v. Tex. Air Control Bd„ 852 S.W.2d 440, 444 (Tex.1993). If a party lacks standing, a court lacks subject-matter jurisdiction to hear a case. Id. According to the Topes, an objection to standing may only be resolved by summary judgment. The Topes argue, because standing can only be raised by a motion for summary judgment, the trial court erred in hearing the motion to dismiss without the twenty-one-day notice required for a summary judgment motion. In addition, the Topes argue that standing is not an issue which can be raised through a motion to dismiss and that a dismissal is an inappropriate means to decide the merits of a case.
The Topes cite Gordy v. Alexander, 550 S.W.2d 146, 149 (Tex.Civ.App.-Amarillo 1977, writ ref'd n.r.e.), overruled on other grounds by statute as stated in Bank of Southwest, Nat’l Ass’n v. Stehle, 660 S.W.2d 572, 573 (Tex.App.-San Antonio 1983, writ ref'd n.r.e.), in support of their proposition that standing can be challenged only by summary judgment. In Gordy, the Amarillo Court of Appeals held that standing could only be challenged through a motion for summary judgment. Gordy, 550 S.W.2d at 149. The Topes contend they were entitled to twenty-one days’ notice of the hearing pursuant to Rule 166a(c) of the Texas Rules of Civil Procedure applicable to summary judgments. See Tex.R. Civ. P. 166a(c).
While the issue of standing can be brought in the form of a summary judgment, standing can also be raised by other procedural means. Bland Indep. Sch. Dist. v. Blue, 34 S.W.3d 547, 554 (Tex.2000); see In re Pringle, 862 S.W.2d 722, 724 (Tex.App.-Tyler 1993, no pet.); cf. Caso-Bercht v. Striker Indus., 147 S.W.3d 460, 463 (Tex.App.-Corpus Christi 2004, no pet.) (standing challenged by summary judgment). Since Gordy was decided, the Texas Supreme Court has specifically authorized standing to be challenged through a plea to the jurisdiction. See Blue, 34 S.W.3d at 554.
CPS’ motion to dismiss is in essence a plea to the jurisdiction.3 A motion should be construed by its substance to determine the relief sought, not merely by its form or caption. Surgitek Bristol-Myers Corp. v. Abel, 997 S.W.2d 598, 601 (Tex.1999). In its motion, CPS argues that the Topes lack standing under the Texas Family Code to bring the petition for adoption. “Whether a determination of subject-matter jurisdiction can be made in a preliminary hearing or should await a fuller development of the merits of the case must be left largely to the trial court’s sound exercise of discretion.” Blue, 34 S.W.3d at 554. Rule 166a does not apply under the circumstances of this case.
The Topes also argue that a motion to dismiss is an inappropriate method to resolve the merits of a case and that the trial court erred in dismissing the suit because standing is not a basis for dismissal under the Texas Rules of Civil Procedure. See Tex.R. Civ. P. 150-165a. The Topes are correct that dismissal is an inappropriate means of deciding the merits of a case. See Lane v. Baxter Healthcare Corp., 905 S.W.2d 39, 41 (Tex.App.-Houston [1st Dist.] 1995, no writ); VanZandt v. Holmes, 689 S.W.2d 259, 261 (Tex.App.Waco 1985, no writ). However, a decision *870concerning whether a party has standing is not a decision deciding the merits of a case. See Blue, 34 S.W.3d at 554. “A plea to the jurisdiction is a dilatory plea, the purpose of which is to defeat a cause of action without regard to whether the claims asserted have merit.” Id. Without subject-matter jurisdiction, the trial court must dismiss the case. Am. Motorists Ins. Co. v. Fodge, 63 S.W.3d 801, 805 (Tex.2001). Dismissal is the appropriate disposition when a party lacks standing; it is not a decision on the merits of the case. We overrule the Topes’ first point of error.
The Topes Failed To Raise A Fact Issue Concerning Substantial Past Contact
The Topes argue, in their second point of error, the trial court erred in concluding they lacked “substantial past contact” with the children.
We will review de novo the trial court’s ruling.4 In Tex. Dep’t of Parks & Wildlife v. Miranda, 133 S.W.3d 217, 226-27 (Tex.2004), the Texas Supreme Court explained the appropriate standard of review when evidence is presented in support of a plea to the jurisdiction.5 Whether a court has subject-matter jurisdiction is an issue of law, which is reviewed de novo. Tex. Dep’t of Transp. v. City of Sunset Valley, 146 S.W.3d 637, 646 (Tex.2004); Miranda, 133 S.W.3d at 226; Tex. Natural Res. Conservation Comm’n v. IT-Davy, 74 S.W.3d 849, 855 (Tex.2002); see SSJ-J, 153 S.W.3d at 134 (standing to bring an original suit affecting the parent-child relationship reviewed de novo); Chavez v. Chavez, 148 S.W.3d 449, 455 (Tex.App.-El Paso 2004, no pet.) (standing to intervene reviewed de novo). When a plea to the jurisdiction challenges the existence of jurisdictional facts, courts should consider relevant evidence submitted by the parties if necessary to resolve the issues raised. Miranda, 133 S.W.3d at 227. The trial court should examine the relevant evidence to determine whether a fact issue exists. Id. If a genuine issue of material fact exists, the trial court should not grant the plea to the jurisdiction and the jurisdictional issues should be resolved by the fact-finder. Id. at 228. Any fact issue must be settled by the jury. See County of Cameron v. Brown, 80 S.W.3d 549, 556 (Tex.2002). However, if the relevant evidence is undisputed or fails to raise a fact question on the jurisdictional issue, the trial court rules on the plea to the jurisdiction as a matter of law. Id.
*871Standing to file an original petition for adoption is statutorily defined under the Texas Family Code. Section 102.005 provides:
An original suit requesting only an adoption or for termination of the parent-child relationship joined with a petition for adoption may be filed by:
(1) a stepparent of the child;
(2) an adult who, as the result of a placement for adoption, has had actual possession and control of the child at any time during the 30-day period preceding the filing of the petition;
(3) an adult who has had actual possession and control of the child for not less than two months during the three-month period preceding the filing of the petition; or
(4) another adult whom the court determines to have had substantial past contact with the child sufficient to warrant standing to do so.
Tex. Fam.Code Ann. § 102.005 (Vernon 2002). The Topes contend they have standing to file an original petition for adoption because they had “substantial past contact” with the children. We emphasize that, under Section 102.005(4), the
Topes have the same status as any adult with “substantial past contact.”6
What constitutes “substantial past contact” is not statutorily defined, and our search of the caselaw has not revealed any easelaw definition. Noting that other subsections of the Texas Family Code require “possession and control,” the Tyler court has interpreted “substantial past contact” as not requiring control over the child. Rodarte v. Cox, 828 S.W.2d 65, 69-70 (Tex.App.-Tyler 1991, writ denied). Although the Topes urge this Court to develop a standard for evaluating substantial past contact, we decline to do so. The existence of “substantial past contact” is inherently a fact-intensive inquiry for which it will be difficult, if not impossible, to formulate a concise standard or comprehensive factors. We agree with the Tyler court that the Legislature intended the standard to be flexible in order to deal with “inevitable situations which could not be otherwise anticipated by the drafters.” Id. at 70.
Although the Topes presented evidence of the difficulties in maintaining contact with their grandchildren,7 we believe our inquiry should be focused on the amount of actual contact which occurred, *872rather than the difficulties encountered in maintaining contact. The focus is on the amount of contact the children have had with the adults. While the Topes may well have done the best they could in maintaining contact with their grandchildren, the fact remains that the actual contact was extremely minimal. The Topes exchanged correspondence8 and monthly telephone calls with Cole and her children. Specifically, the Topes would send gifts and cards for various occasions and holidays. Most of this correspondence could be more fairly characterized as contact with the mother rather than contact with the children, particularly considering the ages of the children.9 The Topes had only physically met their older grandchild on two occasions and had never seen their younger grandchild. Lindsay testified she was not even aware she had a second grandchild until March 2004.
Under any conceivable definition of “substantial past contact,” the Topes lack substantial contact with the children. “Substantial” is defined as “of ample or considerable amount, quantity, size, etc.” Random House DictionaRy of the English Language 1897 (unabridged 2nd ed.1987). Even assuming the facts alleged by the Topes are true, the evidence does not raise a fact issue on substantial past contact. Texas cases in which substantial past contact has been found have involved considerably more contact than the contact alleged in this case.10 The Topes had only met the older child twice, and were not even aware their daughter had another child until March 2004 after the children were in custody of CPS. Although there was evidence of telephone calls, cards, and letters, such interaction is too minimal under the circumstances of this case to create a fact issue concerning substantial contact. Even when viewed in a light most favorable to the Topes, the Topes did not have substantial past contact with the children as a matter of law. We overrule the Topes’ second point of error.
Because the Topes Lacked Standing as a Matter of Law, There is no Need to Decide Whether Trial Court Abused its Discretion in Holding the Hearing Before Discovery
In their third point of error, the Topes argue the trial court erred in holding a *873hearing before discovery occurred. Because the policy behind discovery is to prevent “trial by ambush,”11 the Topes argue the trial court abused its discretion in ruling on the issue of whether CPS withheld consent without good cause before discovery.
If the party has standing under Section 102.005, the party may still not be eligible to file an original petition. If both the child’s- parents have had their parental rights terminated, standing to file an original petition for adoption is limited by Section 102.006. Section 102.006 provides:
(a) Except as provided by Subsection (b), if the parent-child relationship between the child and every living parent of the child has been terminated, an original suit may not be filed by:
(1) a former parent whose parent-child relationship with the child has been terminated by court order;
(2) the father of the child; or
(3) a family member or relative by blood, adoption, or marriage of either a former parent whose parent-child relationship has been terminated or of the father of the child.
(b) The limitations on filing suit imposed by this section do not apply to a person who:
(1) has a continuing right to possession of or access to the child under an existing court order; or
(2) has the consent of the child’s managing conservator, guardian, or legal custodian to bring the suit.
Tex. Fam.Code Ann. § 102.006 (Vernon 2002). CPS argues that the Topes lack standing because the children’s parents had their parental rights terminated before the suit. However, CPS could consent to the adoption under one of the exceptions to this limitation on standing. The Topes argue that CPS is withholding consent without good cause and that the trial court should have waived the requirement of consent in the best interests of the children. See Chapman v. Home, 561 S.W.2d 265, 267 (Tex.Civ.App.-Fort Worth 1978, no writ) (interpreting former Section 16.04).
Our disposition of this matter obviates the need to address this point of error. Section 102.006 merely bars certain parties from filing suit who would otherwise have standing to file the suit. See Tex. Fam. Code Ann. § 102.006. Because the Topes lack standing, as a matter of law, under Section 102.005, there is no need to decide whether Section 102.006 prohibited the Topes from filing an original petition for adoption. Further, there is no need to decide whether the trial court abused its discretion in ruling on the motion before discovery because the Topes would not have standing under Section 102.005 even if an exception to Section 102.066 applied.
Conclusion
We agree with CPS that standing, as a component of subject-matter jurisdiction, can be challenged by procedural means other than summary judgment. Even when viewed in a light most favorable to the Topes, the Topes failed to raise a fact issue concerning whether they had substantial past contact with the children they sought to adopt. The trial court did not err in ruling, as a matter of law, that the Topes lacked standing. For the reasons stated, we affirm the judgment of the trial court.