Anybody know anything about SSI share of cost?

My son has SSI and he just moved back home in march and just wondered if anybody knows how they figure out the monthly share of cost? They are giving him less and I just don’t understand why there deducting 260.00 out of checks. I am becoming his payee soon and I had to give them amount of monthly mortgage and utilities we pay but I think maybe they don’t think he is paying his share of cost. I cannot work because he needs supervision and someone to stay with him most of the time. I may be getting In home supportive service for him and if I qualify than I might be able to be the caregiver or hire a caregiver for him. I had to answer a lot of questions to SSI and they asked me if I work . Does anybody know if I’m not working and my husband pays all the bills, would my sons share of cost be divided into 4,3 or 2? Is this normal that SSI gives less young adult living with parents less amount for rent? I just wanted to make sure he is paying his share of cost and having enough money for his own food and spending money…

If the person is living with someone who is a source of income, they do deduct. Really don`t know the amounts. My son is getting an extra $100 taken out for medical insurance at the moment.

I have no experience with SSI. I’m in Canada. I’m thinking that some of the standards are probably the same though. My son is down as paying room and board which is different from paying rent and bills. He rec’s less then his friend across the hall who is I guess set up as paying rent as he also has bills in his name that he pays and buys his own groceries etc. If your son does not have bills in his name and is not self-supporting then I’m guessing that may automatically categorize him as room and board. I know there is a maximum for room and board here regardless of what our expenses are.