I'm owed $260, but odds of me receiving it are slim. It was some stock the my grandparents bought me when I was little, and the company went under back around 1980, so the stock value was converted to cash. I actually knew about this at the time, but my parents could not figure out how, or bother, to claim it. It's in both my name and my dad's, and they require both names to sign for the property in separate forms, but I haven't spoken to that guy in many years, and have no wish to start now for $260. Of course there is an illegal/unethical solution for that, but...
Really it's only illegal/unethical if your father would object to your claiming the money, or if your signature and the one you sign for your dad look too similar. I wouldn't sweat it and go ahead and collect your $260.