Legally, she could make him the beneficiary, give him keepsakes or possessions, and pay expenses for him (or let him pay them with her credit card), etc.: it was her money and possessions, after all, and she had the right to decide what to do with them, even if you find it strange or odd that she'd leave it to him.Of course, he could not commit fraud--such as changing beneficiaries without her approval or permission--or trick or force her to give him money or possesions. But the problem you face is that if you (or more properly your mother-in-law's estate, assuming your spouse gets appointed the estate's "personal representative" by the court and so has the authority to act on its behalf) sues him on the grounds that you believe he obtained these things by fraud, coercion/duress, forgery, etc., you, as the one suing him, would have to prove your case; that is, you would need actual evidence, not merely suspicion, of his wrong doing. Without evidence, you cannot win.