It sounds to me as if your mil was upset by her adult sons for the jokes at her expense but felt unable to express this. Yet when your ds said something, being only a child, she gave herself permission to really let rip all of her pent up anger and rage. On him. A child. How inappropriate.
As a pp stated, your dh is the scapegoat and bil the golden child and your ds is scapegoat by extension.
She was unable to accept his apology as she was in narcissistic rage. That is to say she felt her whole sense of being at risk of being shattered so she went off and there was no return until she felt your ds was sufficiently admonished. Perhaps he still hasn’t been sufficiently admonished and she may yet continue this rage the next time your ds sees her through pa remarks. www.livestrong.com/article/103707-causes-narcissistic-rage/
www.sott.net/article/153745-Hurting-you-isnt-something-narcissists-do-by-accident
I’ve had this with my mother. I stood up to her and told her in no uncertain terms that access to my dd is a privilege, not a right. Your dh also needs to stand up to his parents and tell them their behaviour is highly unacceptable if they bring your ds’s behaviour up in conversation again. Either ask them to leave, put the phone down or leave yourselves.
My dd (9) is an only child. She desperately wants more family. We tried for for years and years to have a relationship with my brother and his wife. We have been nc since earlier in the year as dd and I are both petrified of them, especially my brother, who is violent. She has psychopathic traits.
My mother is the archetypal, matriarchal, misogynistic narcissist and my brother is the golden child. She doesn’t want accept the nc situation and blames me for my brother’s violence. My fil has, I strongly believe, undiagnosed SN. He doesn’t bother much about dd because he doesn’t know how. Dh is an only. From both sides of immediate family, we therefore don’t have one uncomplicated relationship. We are pretty much on our own.
I am glad you have decided to let him keep the present.
Your ds owes no apology. It is rather the other way round. Under the circumstances, I would think long and hard about sending thank you note as it will be seen as another sign of appeasement.
Would your dh call them instead and feign concern for her as she was so disproportionately angry the last time you saw her? Or would you rather leave all contact. If he does call her, he can also say your ds appreciated the present and leave it at that.
I have taught dd about tall children. That is people wearing adult bodies, who haven’t yet grown up. Adults should be loving and caring. They should be considerate of children. Tall children aren’t. Because their mummies and daddies didn’t teach them lots of things they needed to know about being grown ups therefore they act in mean ways.