Oh dear, oh dear, oh dear, what a dreadful state of affairs. You have done your utmost to be a good DiL, a good, kind and caring wife and a brilliant Mum. I would just step back and let them get on with it and put some space between you, the children and them for everyone's sake. I am sure your DH knows where his true allegiance lies and eventually it seems he will have to make a choice, however hard that might be. My own DD has similar but not so desperate problems with her inlaws; she keeps her distance each time there is a flare up and eventually they see reason and gradually become bearable again, but it's hard work teetering on the edge all the time. I doubt it, but I hope they will see sense and accept you as they bloomin' well should. 
Found out today, can't take it in
Well, that was a farce.........




