I’d keep away too. To me it sounds like your father is under tremendous stress and he felt very upset to be questioned on his own turf by an outsider, which is family dynamics can be something not so obvious. Keep away and let things blow over, he needs to calm down in his own way

Stand by your husband, your Dad was out of line and needs to apologise.

Wow, you have way more self control than me...I would have told my father as we were leaving that he won't be seeing us again until he apologies and addresses his own issues. What kind of grandfather threatens to kill his grandbabies father in front of them? That is not the kind of behaviour that I would want modelled by the adults in my kids lives.

Your father and husband are adults, they can figure it out but what about your kids? I'd be having a talk to them about what happened. Not the actual story being it but how or why some adults do the things they do. I hope the old farts can get through this. Good luck x

I would be letting my father know I won’t be exposing my family to those attacks again. I would also suggest he has a health check if this is really out of character - perhaps it’s a symptom of something.

Your dad overstepped the mark and should never have insulted your sister in front of wider family. Your husband probably shouldnt have lost his temper, but he was right to not sit there and say nothing.
Probably better to keep away from your Dad until he apologises.
If you had taken your Dad on, you might have heard all sorts of awful things he thought of you !

I have been through these sorts of issues, with my mother saying dreadful untrue things to my brother about me behind my back, when I dug my toes in and told her not to interfere in my disciplining of my son. (she was constantly undermining, telling my son he could do what he liked, didn't have to listen to me .... etc, etc.).

I had nothing to do with her for years as she was too damaging an influence.
And if I had known what poisonous things she said to my brother I would never have spoken to her ever again.
It only came out recently.

What would you want your husband to do if his mother attacked you?

I would let it cool down first and then broach the subject with your husband. Sometimes when there is drama it's best in just removing yourself and leaving not to get involved. Your sister is a big girl