Autonomously fighting loved ones

I'm having this happen in my vampire family in Oasis Springs. I just have base game, Holiday, and Vampires. The sim doing it does NOT have a hot-headed trait. He doesn't have any negative traits. He's not mean or evil or anything. He will randomly start fights with his son or grandsons when both are very happy, and take their relationships from half-full green to half-full red in one interaction. He's been alive a long time and has high skills and such, but I still don't see why/how he can do it in a good relationship and mood, under circumstances when the game wouldn't let me select a vampiric fight manually. It takes a long time to build relationships back up when this happens.