Regarding the grandmother whose son is still living, she was the first grandmother to whom the Messenger of Allah ﷺ granted a sixth share of inheritance while her son was still alive.
حدثنا الحسن بن عرفة حدثنا يزيد بن هارون عن محمد بن سالم عن الشعبي عن مسروق
في الجدة مع ابنها إنها أول جدة أطعمها رسول الله ﷺ سدسا مع ابنها وابنها حي
No references are available.
[Its isnad is daif]. Muhammad bin Salim is daif, as stated in Taqrib and elsewhere.