Well my FIL died in 2007 after 3yrs of chemo, this was a big part in my H's MLC. Both my parents died too between 2005 and 2008. So now there is just MIL and my H went to live with her. At BD in Jan 2010, I told her that her son had been having an affair, and she was horrified; ready then to go and slap the OW. Things have changed since then.
Her son moved in with her in Feb 2011 after I discovered affair again (he said it had ended) this time she has sympathy for him, and has even got angry with my two D's because they haven't asked after him when they saw her. When he moved in with her he told her all sorts of stuff which wasn't true, and she believed him. Her relationship with me has changed, and mine with her too. She doesn't come here without being invited and often refuses invitations. I don't call in to see her either, because H is often there.
One of our friends asked my MIL recently, "isn't it kind of strange having your 50 year old son living with you?' Her reply, ... 'its fine, he's no trouble' I think she likes having him there, he does stuff for her and is company for her too. She always did spoil him (he's an only child) and she still does everything for him ( I didn't, I treated him like a grown up!)
So no matter what happens, my relationship with MIL will never be the same, sad for everyone concerned. Even my two D's have changed a bit in their attitude towards her, as they perceive her closeness to her son, whereas she was so close to them before. It can never be the same. I know if his father was alive, he would have had a different reaction to his son abandoning his family, even though his dad was a selfish man, he never did what his son has done.