Q: The first issue:
Three friends, who are not relatives, are partners in the ownership of sheep; they have 20 sheep each. They agreed to gather their sheep in one barn with one shepherd. They are equal in everything. (Part No. 8; Page No. 42
A:
Mixing the sheep between the partners as you mentioned in your question renders Zakah obligatory on these sheep if their total number reaches the Nisab and they graze all or most of the Hawl (one lunar year calculated from the time a property reaches the minimum amount upon which Zakah is due). Each partner has to pay according to his share of the total number of sheep. If one partner has only one sheep and the other has thirty-nine sheep, the owner of the one sheep is to give 2.5% of the sheep required as Zakah and the rest (97.5%) of the sheep is due on the owner of the thirty-nine sheep. This is according to the saying of the Prophet (peace be upon him):
Neither the separate (flocks) may be brought together nor the joint (flocks) may be split so as to avoid Zakah. Regarding that which belongs to two partners, they can make claims for restitution from each other fairly (according to their shares).
(Related by
Al-Bukhari in his Sahih [Authentic Hadith Book] on the authority of
Anas [may Allah be pleased with him])May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.