@Publisher I believe this case is a non issue. It’s a non custodial parent and an account of convenience. They are not spouses.
He is not adding to or using the assets. I would simply have my name removed ASAP. Open a new account with mom and put in an insignificant amount that covers the usage for the student. Imho.
Real estate is trickier and it involves net equity involved and it is not usually owned as jwros with multiple parties and is not a good comparison. Or it shouldn’t be. Your piece of the real estate asset not owned as a joint asset is separately transferable at death, probate eligible, part of your taxable estate in most cases.
This is why I always advise clients who wish to have bank accounts go to a certain person consider totten trusts or POD as an alternative to adding them to your account- unless there is a valid reason to need a co owner. Better to consider a POA for day to day help versus hoping the sibling will remember your wishes to divide to your siblings. Also this can be considered a taxable gift at that time for the sibling involved. As mentioned be careful with non spousal additions to bank accounts and real estate to be mindful of gift tax implications.