Texas Family Code 153.002 and 153.003 show that when a Judge is making a decision as to custody (Conservatorship, Possession, & Access) they look to these sections of the Family Code to instruct them on whom to award custody of the child(ren). In fact, the best interests of the child(ren) is usually the primary consideration of the court in determining the issues of conservatorship and possession of and access to the children. The Court cannot consider a party's marital status (or lack of marital status) or their gender in determining who would be the "better" parent. The old saying that Courts favor the mothers is not the case, under Texas law.
Whenever you are framing your case and your arguments, it is usually best to keep this "best interests of the child(ren)" in mind. The Judge surely will. Show the Court how you are the better choice and tread lightly on only showing how the other parent is the wrong choice. Focusing only on the other side's negatives and not enough on your positives will be wasted efforts in the long run. Make the focus your education, training certificates, workplace achievements, awards, community involvement, and support of children's activities. If you do not have these when your case first starts, then there is no time like the present to start building yourself up in these areas. Better late than never.