What do they fight about?
I think my BIL and his wife might be LIE/ESI Duals. Last night, we were over at their place for my nephew's birthday, and at one point my BIL was quite involved in an animated discussion with my FIL and my husband, and his wife wanted to get the party rolling, so she walked by and said to her husband, "okay, time to be a daddy now." My BIL took offense, and they had to go to the back room to argue it out for a few minutes.
I also think my dad and mom might be LIE/ESI Duals. They particularly had some trouble around holidays, or doing anything traditional. Like at Christmas time, it was the tradition for us as a family to act out the Nativity story (and record it on video, every single year,). And various other holiday traditions. I believe all this was mostly driven by my mom. My dad would get all stressed about it, just wanting to hurry up and get it all over with. But we kids would be all over the place, or having side conversations, or whatever, and Dad would lose his cool. Then this would upset my mom, who felt that now the whole experience had been ruined. She'd be in tears, and my dad would get all pessimistic and critical. We somehow always managed to finally carry out whatever it was we were trying to do. But, no holiday ever went by without probably at least one fight.