From the Rulings on the Udhiyah

Question:
We move on to a message sent by the questioner Sa'd Muhammad from Riyadh. He says: Your Eminence! A widow whose husband has passed away has six young children, and she also has a son from another wife. This son is employed, married, and has children. He lives in an apartment, and his aunt and the children live in another apartment, but in the same building. The question is: Is one sacrificial animal sufficient for all of them?

Answer:
No, each person should offer a sacrifice. He offers a sacrifice for himself and his household, and you offer a sacrifice for yourselves, provided you have the ability. This is a recommended practice (sunnah), not an obligation. With the ability, each person offers a sacrifice for himself, his children, and those under his care. And praise be to Allah, it is a recommended practice for a man and his household, and for a woman and her household. So he offers a sacrifice for himself in his apartment and his household, and you do so for yourselves. Yes, the recommended practice is for each person to offer a sacrifice, because you are in two separate households. Yes.

The presenter : May Allah reward you—O Shaykh—and bless you, your knowledge, and the benefit He has given the Muslims through you.