Dad brainwashing son

Hello all,
I was searching the web and came across this site.
My ex just came into my childrens lives after 9 years.He never had
anything to do with them when we divorced and two years later I
feel in love with a man who took on the roll as a father figure in my
childrens lives and has raised my children with me for 7 years now.In
Jan. this year the ex came back around wanted a relationship with the
kids and I was happy to have some time to relax and not have to worry
about them one weekend out of a month ya no....the way it should be.I
thought all was going well until my daughter told me that the dad is
bad mouthing me and my husband to the kids calling us all sorts of
names and saying it is my fault he was not around all the years.
He has stoped child support as well 3months ago.My daughter who is 16
says she is not going back to his home because of the constant talk
about how bad of parents my husband and I are and when she has asked
him to stop it is worse.
My son is 13 and was very young when his dad and I divorced so he
doesnt really know him and likes being at the dads home with friends he
has made there.Thing is my son now talks to me like I am trash off the
street yelling at me the way I was treated with his father and when I
tell him to stop he will curse me.
I have tried everything to make my son see that he does not need to
speak to me like this but he continues.His father told me that my son
hates my home and wants to live with him now.....
I am speachless over this news and cant believe it.My daughter thinks
my son will get over this and not to let him go.I do not plan to let my
son go live there but how can you make the ex stop turning the child
against you.My ex should be thanking my husband and I for all we have
done for the children instead of calling us names and acting as a
child.
Sorry this is so long.
I am hopeing someone will have something to say about this.......