Do we really need a 5+ bedroom house?

***please read***

Moving in together is the next step for my boyfriend and I.

I have one child and have full custody with no ex in the picture ( 2 year old girl). He has 3 kids. Twin boys who are 7 and a girl who is 4

He shares custody. His ex doesn't work (by choice...she told him she would make more money off him if he was stupid enough to leave her and that she would be richer with all the money he'd have to pay her)

She has them more right now. He is fighting for more access. He wants at least 50 50 but really want sole.

Right now he works like crazy supporting everyone and paying lawyers. So he only has the kids every other weekend. Friday evening to Sunday evening. Twice a month basically.

He wants 5-6 bedrooms in order to have the most space for the kids. I said that since they don't live with us full time that we could have kids double up and share and make it work with 3-4 bedrooms instead. Have the girls and boys share. Save us some money instead of investing in the biggest house when all of us won't be together all the time 24/7.

Please note we are renters at the moment. And in our area 3-4 bedrooms run about $2000 a month. 5-6 run about $3500.