Legal Question in Wills and Trusts in Texas

You've actually asked 2 questions, but both of them are equally important. First, the father could leave his estate to whomever he chooses. One son, three sons, or no sons at all. Texas has no forced heirship, and the Will can leave property to any person(s) of the father's choosing.

Second, there are many reasons why a Will might be contested. In the end, they all come down to a lawsuit, evidence and the judgment of a judge or jury. If the contest loses, the Will is upheld and the son stays in the house that he now owns. If the contest prevails, some or all of the Will might be thrown out, and the son might lose the effect of the gift under the Will.