<human>: Condense the text into a few key points

So I started a new job and two of the workers are sisters. These sisters have some major sibling rivalry going on. I guess when they were younger they were split apart. One, K was raised with her brother and her bio Mom. The other sister and her twin were raised by a distant family member. 

This definitely causes strain in their relationship. I can see it in how they interact with each other. They also both come to me to vent about the other and I am not sure how to tell them to stop. I really like them both and I would like to be supportive of each of them, but I don't know how to do that in this environment.

I want to remain professional, but the work environment I am now in is very casual. Everyone is friend family or foe (sometimes a combo) to each other.

How do I handle this? They just had another argument and they both are coming to me separately to debrief about it.

I am definitely never going to be management material...
<bot>: I work with two sisters with MAJOR sibling rivalry going on. How do I handle it when they both come to me to complain about each other?