I agree with the other attorney who answered that you are rushing to judgment by assuming your ex husband does not have signature power on the bank account or that he is not the "real owner" of the account. Who is the source of the money in the account on which those checks are written? Your ex? Or does it come from the son? Is he signing the checks in his son's name or his? If you think he might be stealing his son's money, you should contact the son and ask him if he knows about the accounts and the checks your ex is writing. Just because he may be committing fraud or identity theft by opening a bank account under names other than his does not make you a party to "forgery" unless you were in on the scheme for him to steal money from his son or hide money from his creditors. Assuming you were not in on any schemes, it is highly unlikely you would face "legal charges" assuming you mean criminal charges. On the other hand, it is possible you could be made the subject of attempts by his creditors to disgorge some or all of money he paid you on some kind of fraudulent transfer theory. More facts would be needed in order to assess your risk of liability as a recipient of potentially fraudulent transfers.
Accounts can have several signers, named on the check, or not. Are you sure he isn't authorized to sign the checks he is presenting to you? Is he signing his own name? Or is he signing his son's name? Also, if his son't name is being signed the check, are you sure the son isn't the one who is signing the check?
The above is not intended to be legal advice, but may be used for general information. Please contact an attorney for specific help tailored to your needs. www.figgardenlaw.com