My son is 10.
The Ex-Wife cheated twice during our 14 year marriage.
Divorce ensued instantly upon this discovery, and no alimony was entitled to her (as per the local laws of the country.)
Although she walked away with 100% ownership of a profitable company we co-founded, her parents felt she was still entitled to receive an alimony payment, even though they acknowledged her wrongdoing, and therefore decided to close all ties with me and my family.
Since the divorce our son has taken it upon himself to consistently attempt to include me in all of her family's events (Xmas, vacations, etc.) and he even ends every call with grandma with a, "Hey do you want to talk to Dad?" she stone-cold says, "NO."
Up to this point, he thinks everyone is still friends and the love he has seen between all family members is still there, as I continue to show nothing but love and respect to all.
Now however, he growing very suspicious and can't reconcile why her side of the family suddenly went cold. It will be very soon before he starts asking hard questions.
Knowing this, how can she and I collectively explain to him this new inter-family protocol (which they set), without getting into the dirty details of the divorce?