Legal Question in Civil Litigation in Texas

Probably.

It is not a contract:

1. If the object of the agreement was illegal. A contract to commit murder is void.

2. If one of the parties is insane, delusional, or is a minor.

3. If the terms of the contract are too vague ("Joe promises to be mostly nice to Bob's sister and not hurt her feelings if Bob will give him $50" or "Joe promises to fix the roof pretty soon and not charge too much for it").