(a) In addition to the general standing to file suit provided by § 102.003, a grandparent, or another relative of the child related within the third degree by consanguinity, may file an original suit requesting managing conservatorship if there is satisfactory proof to the court that:
(1) the order requested is necessary because the child’s present circumstances would significantly impair the child’s physical health or emotional development; or
(2) both parents, the surviving parent, or the managing conservator or custodian either filed the petition or consented to the suit.
(b) An original suit requesting possessory conservatorship may not be filed by a grandparent or other person. However, the court may grant a grandparent or other person, subject to the requirements of Subsection (b-1) if applicable, deemed by the court to have had substantial past contact with the child leave to intervene in a pending suit filed by a person authorized to do so under this chapter if there is satisfactory proof to the court that appointment of a parent as a sole managing conservator or both parents as joint managing conservators would significantly impair the child’s physical health or emotional development.

(b-1) A foster parent may only be granted leave to intervene under Subsection (b) if the foster parent would have standing to file an original suit as provided by § 102.003(a)(12).
(c) Possession of or access to a child by a grandparent is governed by the standards established by Chapter 153.