A lot of my friends disagree with me, but that, to me, is the one thing I cannot abide -- exposing the children to the OP. Introducing the kids to someone you're romantically involved with is bad enough, especially before the D (!), but the very person that helped break up the family is beyond the pale.
In older days, a lady's brother(s)/male relations would drag the curr out into the street and publicly flog him for so disgracing their sister and their family.