I would agree with Davida1968 the current atmosphere in the household will be affecting the children adversely. Is it your SiL who is insisting that them staying together is important for the children?
You say he is controlling, I get the impression that making everything look OK is an obsession. I think for your daughter and DGC's safety, he should be told to leave the home now. If necessary get a court order and then make sure that for the foreseeable fuure - that may not be that long, your daughter and grandchildren always have a member of their wider family living with them.
Govt announces Ukrainian style scheme to bring thousands more migrants to UK

