Do my horses need blankets?

Ok so I have a QH mare that's 13, an Arabian mare that's 20 (but she's in really good shape for 20), an X-race Thoroughbred that's 7, and he's just a little bit hard to keep weight on. there always outside but I bring Roman (the x-race horse) into the barn on really cold nights. have a shed but Roman likes to kick White(the Arabian) out sometimes.... and I live in Iowa so it's really cold and snowy in winter. and I was just thinking if they need blankets this winter? and if so what kind? thank you so much!! :)