Allies and Capital Ship XP

Today, during an epic 7 hour game with two friends and a bot, the one friend who was my ally and I got into an argument as to whether or not allies split xp when both have cap ships in a gravity well. We both had three capitals on a planet, mine all level 1 with no xp points yet. He had one with no xp as well. He claims that as allies we split all xp gained in combat evenly, i.e. only half what we'd get if it was just one of us. I think this is wrong. All my ships gained 709 xp, while his gained something more like 690 ish. With the discrepancy, I believe I'm getting xp not only off of destroyed enemies but the stuff he loses as well. From what I've seen here, I gain xp from the death of anything I don't own, which would include my ally's stuff. So the real question: how is the xp of the stuff that isn't owned by either of us divided?