Is it permissible for a son to share with his mother one portion of a large ox sacrifice in which seven people are participating?

It was narrated from Ata' bin Yasar, from Abu Ayyub al-Ansari, that a man in the time of the Prophet, peace be upon him, would sacrifice a sheep on behalf of himself and his household, and they would eat and feed others. This is evidence that one sheep, or one-seventh of a camel/cow, is sufficient for the members of a single household. So, if a man and his mother live in the same house and the provider is one, one-seventh of a cow is sufficient for both of them, with the emphasis that the cow must have reached the age of sacrifice, which is two years or more, based on the saying of the Prophet, peace be upon him: "Do not slaughter anything but a musinnah (an animal that has reached a certain age, usually referring to a mature animal)."