Our relationship with them was always rocky and finally ended when DCs were 6mo & 2yo. I was sad that DCs were losing GPs, but DH felt only relief and it has to be said that life is so much easier and happier without them.
The only contact since them has been birthdays/Christmas when they send a generous amount of cash for each DC. To begin with I banked it for them and sent a thank you myself, but as DCs got older, they opened their own mail, were aware of the gifts and now always write their own thank you.
Therefore, they are aware DH has living parents. But they have never asked why we don't see them. They are 10 & 12. Do you find this odd?