The Texas Family Code Section 2.102 controls - Parental Consent for Underage Applicant. Since your parents are separated in the State of Texas, they are still married. Either can give their consent to your marriage, unless the temporary orders in their divorce state otherwise. You will need a certified copy of the temporary orders in their divorce for the clerk to review. However, if either parent does not approve of the marriage license, they can go to the court that controls their divorce and ask that the judge ask that the other parent not have the authority to allow you to marry. In summary, your marriage might be invalidated by the judge in your parent's divorce. So I would encourage you to have both of your parents sign the paperwork agreeing you to marry.
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