So this is my first post, guess I should give a little background. First of all I have 2 DS 15 and 16 that I was a single mother for many years and while I know I'm not even close to perfect I feel that I have managed to raise 2 fairly responsible children. (I.e. neither of them have ever come home drunk, had any trouble with the police, repeated a grade, or had any major trouble at school. The worst was a short streak when youngest tried skipping classes a few times got caught and was punished.) 

About a year and a half ago I reconnected with my youngest son's father and we started dating again. 8 months ago we decided to move in together and 2 months ago we purchased a home together. Youngest son was ecstatic because he had not had a previous relationship with his father. The thing is in the 14 years we were apart he had 2 more children who's BM abandoned them when the youngest was less than a year old. I do give that situation full credit for FDH growing up and really becoming a parent. 

So now I am "mom" (yes that's what they chose to call me) to my son's younger 1/2 siblings. And for the most part it's pretty good. However here comes the twist..... MIL from he'll!

She regularly wants to undermine, go behind our backs, tell skids to lie to us, break all the rules we have set,  and generally just do whatever she wants with out a thought for anyone else. She feels that because she helped FDH by watching the kids after BM left so he could work that they are somehow her children. Also it does not help that BM signed TEMPORARY guardianship papers 7 years ago over to her and she tells everyone who will listen how she is forced to raise her grandchildren.... yeah the ones that live with us.

I could probably write a book of examples of her bad behavior when it comes to the kids but the most recent was last night. It's DSS b-day and FDH and I needed to pick up his present and then we both had to work today so she offered to keep the kids. I thought well maybe she is being nice, yeah right, we got a phone call at 10 pm last night saying she couldn't keep the kids today and doesn't like driving to our new house because it's too far (literally less than 10 minutes from her house) and besides she doesn't like our road so we will need to pick them up in the morning and take them to work with us and btw would we like to talk to them? (They are 8 and 9 and still awake. Bedtime is 8:30 and she knows it.) Then she tells SD to make sure not to tell us she lets them stay up as late as they want at her house every time they sleep over. Needless to say FDH was very unhappy too and says no more sleep overs. Now what do I do about the rest of her bulls$$! Behaviors?