All perfect praise be to Allah. Blessings and peace be upon Prophet Mohammad and upon his family and companions.

If the Udhhiyah (sacrifice in Eiduladha) was a sheep, then the reward is attained by its owner and his household whom he supports. But, if it was a cow, or a camel, then seven persons can share it and attain the reward.

Al-Khteeb Ash-Shirbini (May Allah have mercy on his soul) stated: “Seven persons attain the reward if they sacrificed a cow, or a camel as an Udhhiyah.  This opinion is based on what Muslim reported from Jabir (may Allah be pleased with him) who said:" We, along with the Prophet (PBUH), slaughtered the camel on behalf of seven persons, and the cow as well) Evidently, the seven people weren`t from the same household…… the reward for offering one sheep as an Udhhiyah is attained by its owner, but it is permissible for him to offer it on behalf of himself and his household, or on behalf of himself and let others share the reward." [Moghni Al-Mohtajj].

Therefore, it is impermissible to share one sheep as an Udhhiyah. The alternative is for the person who wants to share the Udhhiyah is to make a payment as a gift, and not as a share. In fact, a gift has its reward from Allah The Almighty. And He knows best.