@mikolokoy There's not much interaction. After all, it's not like some God grabbed two souls, and forcibly stuffed them into a body that already housed third. It actually seems there's no Gods in that world, period.
What actually happened is that Balud, as a child, recalled memories from his last two past lives, (possibly because of his mother's training trauma) and as a result went insane. The two other guys are more like delusions than actual souls, made up by his brain to cope with experiences that would otherwise consume his existence - likely because both had extremly strong, even obssessive regrets before they died. To help maintain his remaining sanity, the other personalities agreed to minimize both interactions and the time Balud isn't driving the body. Once they get over their regrets, their "screentime" will be even less.
Novel explains this stuff better.