Co-signer and student loan?

my ex and i co-signed for my daugher. my daugher now has a mental disability so i am paying what i can towards her student loan. my ex is counting on them putting a lien on my home as an incentive for me to pay and him not to pay. He makes 3 times more than me and he does not give child support for this disabled daughter because of her age. If I do get a lien can I legally go after him for half of the debt since he is the other co-signer.