I have a question about selling a home... my friends mom and dad are married and both on the title/deed of the house, but his dad thinks that he can sell the house without the permission of his wife and thinks that she has no say in it at all. Is this true? Can he still legaly put the house on the market without even consulting her about it first?

Yes, he actually can put the house on the market, but no, he can not sell the house. If both are listed on the deed, then BOTH are co-owners and both must sign the new deed transferring ownership.

The buyer's attorney is not going let a closing occur without both signatures.