It's complicated but to cut it short, MIL lives alone and FIL lives with SIL. They own two houses.
SIL has a small child and seems to boss FIL about as though his house were in fact HER house. We see her snap and grump at him despite his health being dodgy.
The other day MIL came round and SIL sat in the car outside because her child was asleep.
MIL didnt' stay long ...she was just picking something up...but standing on my lawn she suddenly burst into tears :( and said she wished her relationship with SIL was better and that she was trying to talk SIL into counseling with her because it upset her that they didn';t get on better.
MIL cares for SIL's child three days a week so SIL can work part time and MIL is 72 and still works 3 days herself.
I feel worried about both FIL and MIL if I am honest as SIL seems to be a weight round their shoulders and she's NEVER happy. Walks around agressively and grrumpy all the time. She loses patience with her child very easily too.
What can DH and I do though? We live an hour away from them.