Do you think he'd be open to joint budget/accounts? Is there a reason it hasn't happened yet? Perhaps if you sit down with him and suggest you work on a joint budget, and have all your costs etc there, then work out how much $ for each bill/expense etc. Then you can suggest how to set up your accounts to best cover all the costs and what will need to be put in from each of you to cover it all etc. Maybe going in gently will help if he's been finding it a little hard to take a what's mine is yours approach.