This just makes my heart hurt. I'm so sorry for your bunch. What a complete loser.
My older two kids dealt with this with their birth mother for years. Every time she popped her head up in their lives, they always thought "this time she'll want me, this time she'll love me." She never did. She broke their hearts so many times. Now? They have no contact whatsoever. Stupid bitch. There's a special hell for evil people like them.
Give them some extra hugs and watch out for the aftermath - they're sure to have a lot of anger and hurt from this.
((You and the bunch))