This fact scenario ended up at the The Texas Supreme Court because the District Judge allowed the boyfriend to have visitation with the child. The father and boyfriend filed their briefs. Many Amicus Curiae briefs were filed by non-profit organizations and foundations dedicated to protecting parental rights. One of those organizations is the newly created Texas Association of Family Defense Lawyers (TAFDA) https://www.tafda.net/find-an-lawyer, which I am a proud member. The founding member of TAFDA and I, co-authored an Amicus Curiae brief in response to another foundation's Amicus Curiae brief who argued in favor of the boyfriend having possessory conservatorship of the child and visitation rights.
The Texas Supreme Court, using some of TAFDA's arguments, concluded that "When a nonparent requests conservatorship or possession of a child, the child’s best interest is embedded with the presumption that it is the fit parent—not a court—who makes the determination whether to allow that request." The Texas Supreme Court further ruled that "The trial court thus abused its discretion in ordering, over the objection of [child's] father, that [boyfriend] be named Abigail’s possessory conservator with rights to possession of the child.
The full opinion can be found at: https://www.txcourts.gov/media/1448054/190694.pdf