The khandan (translated as family, clan, or pedigree) refers to the caste system of the Yarsan. There are three castes: sayid سید, mam مام, and the casteless am ئام.
Sayid is the highest caste. Beneath the Sayid are the Mam. The Sayid and the Mam have sacred responsibilities to preserve, perform, teach, and lead the wisdom, poetry, rituals, and beliefs (et alia) of the religion. Congregations must always have a Sayid and a Mam present in order to rightly guide forward in the correct way. In this way, the distinctions seem a benign and efficient way to ensure the transmission of Yarsanism from one generation to the next.
The structure itself reminds me of Judaism, where the Kohanim and the Leviim worked together. The translations reflect this to some degree. Sayid translates as a religious, hereditary honorific also used by the Muslims for anyone descended from Mohamed. With their elevated position, then some ceremonies will be proscribed to all except a Sayid. Mam translates as uncle, and is a secular social honorific widely used by Kurdish people for those in authority (e.g. Mam Jalal, a political leader). This reflects their role -- shared with the Sayid -- in education and guidance.
The way the caste system is maintained reminds me of the Yezidi traditions for their own castes as well (Mir, Shekh, Pir, Murid). Like the Yezidis, intermarriage is forbidden between the castes. And the castes also serves as titles. Sayid is gender-agnostic, so you would say Sayid ____ for either a man or a woman. However, for Mam you say Mam ____ for a man and Mamo Zhin ____ for a woman.
Setting aside comparative religion, the caste system plays out in normal village life. "Mam Dilshad" is the way that my professor in Yarsanism is addressed. I had always spoken to him as "Kak Dilshad" or simply "Dilshad" with no issues but I had always noticed he made an effort to greet everyone and much of the time other people greeted him first. He seemed very well-known and well-liked in all the villages we reached. Then one day something happened and my understanding grew deeper. When we were in his village Tulaban, some little children no older than eight or nine years old came up to the car. They initially called him "Kak Dilshad" -- the generic mister to address someone. Even the secularised, converted Sanaar swiftly but positively corrected the children: Mam Dilshad. It seemed loving and everyone was smiling but it also seemed like an important, potent reminder which the children quickly understood. It was like introducing the children to a relative -- "Don't you remember your uncle? Treat him with respect." Since then I generally addressed him as Mam Dilshad, as part of my education in Yarsanism involved abiding the traditions of the community.
I looked for other ways the caste system works in daily life. Aside from way Mam Dilshad connected people together whenever he visited them, I looked for signs of economic inequalities. However, these were not generally apparent. And the am who I spoke to said the caste system means they must respect the Mam and the Sayid but they are unsure what exactly it means. "If he asks me to do something, I must do it or whatever," said Hunar. "It means I must respect him," said Sanaar with a tone suggesting he viewed it as archaic and dysfunctional. I imagine there must be some cases of forbidden inter-caste love that have happened. And for parents, it must be part of their work in finding spouses for their children that they must ensure the suitor is the correct caste. However, there are surely other factors at work as well in marriage: for example, a poor am family that moved to Erbil and grew rich will surely want to marry into a family (a fellow am of course) that is on equally good footing by secular measurements.
Among the Muslims, there are some issues. Mehmet told me about a major controversy in his family. One of his Muslim Turkoman cousins married a Sayid woman. It was flatly forbidden by her family, but they eloped. There are horrible suspicions and rumours by Muslims surrounding who is a Sayid. The normal and totally false rumour is that on a certain night of the year the Yarsan gather in a temple and have a massive and indiscriminate orgy, and that any child conceived on that night is a Sayid. This makes absolutely no sense and is an example of the ostracisation and constant paranoia-fueled condescension with which Muslim societies regard non-Muslims in their midst. This has also made it upsetting for Yarsan people to be asked about their religion: it opens up all the swirling cesspools of stupid rumours. So if someone Yarsan is asked even by someone with the best of intentions, the rumours are still there filling what is unsaid in the conversation, and they rightly feel flustered, worried, and trapped: the result is a cycle of secrecy and seeming hostility, arousing even more suspicion. (Why are they so upset about being asked questions when there are such obscene rumours, if they are not actually hiding something obscene?) In the end, with respect to Mehmet's cousin, the marriage took place but the Sayid woman does her prayer and conducts herself in complete secrecy, and has (outwardly) forbidden her children to practice Yarsanism. Mehmet said she has taken great lengths to ensure her children are part of the Muslim community with all the benefits that confers, though I suppose whether that is in fact true or false she would be bound to that public image for the safety of herself and her children born to a Muslim father.