ANSWER:

Yes, one portion in a big animal (1/7) is sufficient for the entire family living under one roof and you can include your deceased grandmother in this as well. 

My query is is 1 hissa in big animal sufficient for one family all members who live together and can I do sacrifice on behave of my deceased grandmother as a sadaqah on her behalf will it benefit her.

Slaughtering | August 4, 2019 3:55 am
Previous

On sacrificing a goat or prescribed animals on Eid ul Adha, we sacrifice to Allah on behalf of one or many person, my question if one sacrifice is given on behalf of many, does the reward is getting splitted as many? If 50 rewards in total means, 5 person get 10 reward each? Or each person gets the whole 50 reward? Please clarify
Next

How many days can you sacrifice the animal for eid al-adha? Is it also allowed to sacrifice it on the 2nd day for example?