I split up with his dad in February. Neither of us could afford to move out. His son who is in college turned 18 recently. He's going to university in September. He's just finishing his exams and will be be done with college in a week or two. I've pointed out as now there is 3 adults living here the rent/bills should be split 3 ways. His dad is adamant that he shouldn't have to till he stops getting child benefit/tax credits which is August. The son is currently living on the child maintenence provided by him mum which is quite a lot. I just want to know if I'm being aibu to not want to have to keep subsidising a legal adults bills?