Domestic partnership. can a 16 year old enter a domestic partnership with a 19 year old of same sex

Age is not the relevant problem here. Texas does not recognize the validity of a same-sex domestic partnership. For that matter, Texas does not recognize any domestic partnerships. You are merely roommates.

Since she is 16 and you are within 3 years of her age, you have an affirmative defense to a criminal prosecution. The age of consent in Texas is 17.

She cannot enter into a binding contract until she is 18 years old. A Texas court will not enforce any contract that has been determined to be against public policy.