"sib zeem" is a formal introduction and/or making official of status and bonding, it is often made during weddings and when seeking relatives, in order to know how to address one another. a formal party would be necessary, when a couple has lived together, have children and established a relation as husband and wife but never had done a wedding. it almost like a wedding except there's no negotiation, no monetary exchanges, just a big feast making the two side acknowledge it's unification (as husband and wife) and the bonding of relatives.
"sib zeem kwj tij" is no different except to bonding as relatives due to the same clan name. often times a conversation between two parties is sufficient but a party/feast would be ideal if one person is intending on joining a group.
the best form of "sib zeem" is when you get jumped into a gang...blood in, blood out! ha!