I've always had boars and sows in the same room, and it doesn't seem to make any difference. In one room I have a cage of four boars (living together) and six sows. They can see and smell the sows, but don't seem to care. The only problem I've ever had is babies trying to mount their Moms, but they were taken out before they could do anything, so that problem was solved ;D So I guess it really depends on the piggies and their personalities.
Kimmie