Apologies this will be long - lot of background.... SIL (DH's sister) is considerably older than him. She spent many years in a very abusive marriage before finally getting the courage to kick him out when he started getting physical towards her eldest DD. She has four kids from that marriage.
Recently, she has taken up with a new controlling arsehole man, who is deemed wonderful simply for not beating her up. In all other respects, he's a knob of the highest order - expects to be waited on hand and foot, ignores her kids etc. Based on past experience MIL and DH said nothing and were just welcoming to new man, hoping he'd sort of 'blow over'. Finally (I think knowing they weren't impressed) SIL pushed and pushed them for what they thought and when they were less than fully enthusiastic, she got very very cross and basically said they don't trust her and won't like any man she gets together with. Things have been slightly frosty since, but I still have a good relationship with her and we see a lot of the kids, who absolutely adore DH.
SIL recently announced that she and new man have decided that they are going to up sticks and move 300 miles away, so NM can start his own business