Forgotten Family account info

My brother needs the family account password to be able to sign into his xbox gold account. Problem is, I think my dad had that information, and he's recently had a stroke and can't remember much of anything. I'm 22, and have the information for my other brother's login info, and he's not having any problems because I know all the information to help him with his, but for this brother, I have no idea how to help him. I'm not even certain it's my dad who put in the parent account, but it's the only thing that makes sense. I don't know what to do, my dad's stroke is keeping him from remembering and I have no idea how to fix it without him.