Would you get involved if two adult children were involved in an argument?

[SuperstoreFan]

Basically as the title says.

No I'm not one of the children involved but I'm witnessing the consequences.

Or would you stand on the sidelines and watch your family implode?

I understand that there may be a reluctance to be seen as 'taking sides' but I can't wrap my head around not saying anything and the situation has escalated to threats towards one sibling's family.

DH's family are always falling out with each other. When they meet up, the main topic of conversation tends to be whose not speaking to whom.

Fortunately, DH is not interested and keeps well out of it all.

DH and his sister have fallen out massively - MIL should have intervened due to the nature of the argument, but won't because she relies on SIL for everything (clever move with ulterior motives on the part of SIL). I would like to think I would intervene but at 90 I'm not sure I'd have the energy, to be fair.

It's really upsetting though - we no longer have anything to do with SIL and BIL and our DC have no relationship with them. We're a very small family and before this we were very close, but now there's nothing. God help us if MIL ever needs social or medical care, and after she passes away, as the communication between DH and SIL is non-existent.