Locked out of Steam account because cannot get access to password

My son has a steam account with many games on it. He has lost his password and can't retrieve it because he also doesn't remember which email he used. I do not want people to get a hold of this account and I also want my other son to have access. So how can I get the password and then change it to my own password so I can take control of when they play.I have already tried the lost password we will email it to you. But since he is not sure which one we can't get it.Yes, they are teenagers and of course didn't keep a book of passwords so I was wondering if anybody could help me. Is there a way to get in contact with steam and explain or do we just say goodbye to the hundreds of dollars of games I have purchased over the past year for them to play.My other so is a helper on some of the games and very responsible but our household is in turmoil over this because the boys are fighting over it.Please help!