Grandparents too?  That's pretty sad.

I haven't been through something like this, but I've heard some good advice about it.  Never say bad things about the children's father to them, or they will possibly resent you later.  Tell them perhaps that Daddy is very busy and that he misses them and wants to see them.  Let them work it out for themselves as they get older (and hopefully it won't come to that, because their father will come to his senses).  Be available for them to talk to as they form their own opinions on the situation, but don't criticise the father or grandparents outright.  Help them to get their thoughts straight, answer questions honestly, but don't volunteer extra information.

That's all I can offer - hope it helps.

Why doesnt the father and the grandparents want to to see the kids? Just because the father has a new gf doesnt mean he cuts his kids out of his life.  To me that is horrible. In my situation when i separated temporarily from my husband, he still maintained contact with the kids even when he had his mistress. And i always kept his side of the family informed of the kids when they asked.

Just explain to your kids the situation and that it is not there fault. Dont put the dad down as the dad might change his mind and turn against you saying your the one stopping him seeing his kids. Always maintain with the kids there dad still loves them and maybe has a lot on his mind at the moment. You also need to tell the dad to talk to the kids himself and explain himself to them "why he doesnt want to see them". The kids need to hear it from there dad, not just from you as they seem old enough now to try and understand.

I'm not exactly sure how you can tell them how.  But one thing I know you really have to get it thru to them, is that it's not THEIR fault that he doesn't want to see them.  They didn't do anything, and it was his choice.

Wish you the best