Legal Question in Real Estate Law in Texas

No, just because they contribute help with the payments does not give them any legal rights to ownership of the house. The only recourse they would have against you is some kind of claim for repayment of the money they helped you with but then you would have a claim for rent during the time they lived with you. Essentially, all they are doing is paying you rent in the form of a partial house payment, I would actually have them pay you directly, and then you pay the house payment from your own account, just so everyone is clear that the payments are for rent. It also wouldn't hurt for you to have them sign a lease agreement.

You need to sign a lease with your son and daughter in law making clear that their payments are RENT, not any sort of purchase on time. A lawyer should be able to do a simple lease for you for less than $500.00.