relations between sibling and adopted

What is the name of your state? Texas
ok here it is.
a girl wants to move in with her bf, but lives in a different state.
(both under 18)
to do this legaly, would adoption be right?
and if they did marry would it be legal?
thanks ahead of timw

Adoption is not necessary.

I am assuming she wants to live with him and his parents. As long as she has her parents' permission, then I don't see why anything needs to be done. If she is adopted, then that would make her the legal sister of her boyfriend and then if they ever wanted to marry, the couldn't because they would be legal brother and sister, much less date.

As far as marrying under age without parents' permission, it depends on the age and state.

Adopted siblings marry? OMG!

Sorry, but just the thought of siblings (adopted or otherwise) marrying gives me the creeps.