A clan is a group whose core comprises a number of families derived from a common ancestor and bearing a common surname. Almost without exception, that core is accompanied by a further number of dependent and associated families which can be related to the clan or larger family for various reasons -- such as through marriage or by seeking protection from a larger and more powerful clan or family. Some families which were once recognized as lesser branches in some other clan have since become clans in their own right and many can be related to more than one clan.
In contemporary Hârn, adoption (alienation from one's birth family to join the adopting family) is the most common means by which an individual leaves one clan to join another. Note that this does not create an associated or dependent family within the clan -- the individual joins and takes the surname of the adopting family.
Marriage is the most common means of adopting a family, and its surname, into a clan. The marriage creates the stirps for a lesser or junior branch of the clan, with the dependent family comprising those who are descended from the ancestral clanhead through the female line and consequently bearing a different surname.
Note the distinction -- adoption may change one's clan (alienated from one's birth family to join the adopting family), but marriage does not. The children of the marriage, who can trace lineage to the clan through their mother, are members of the clan; their father remains a member of his own birth clan. Also note that one votes in the succession council of one's birth clan, and not in the clan council of one's spouse.
Members of a family that is a lesser branch of a clan, though bearing a different surname, are full fledged members of the clan and many have succeeded as clanheads and inherited the clan's titles and armorial bearings. In these cases, it is not unusual for the heir to adopt the clan name in place of a birth surname.
The best example has us going outside Chybisa to Kanday. Short version: Andasin IV, head of clan Kand and king of Kanday, is the son of Ranald Milaka. Andasin's birth name, then, is Andasin Milaka and he is a member of a family that technically is a lesser branch of clan Kand. But, as Andasin currently bears the arms of Kand, it would appear he has adopted the clan's name. His siblings are also members of clan Kand, but they still bear their birth surname of Milaka.
Note that Andasin's father, Ranald Milaka, who is head of clan Milaka, is not a member of clan Kand. It is through Andasin's mother, Mirelael Irien, that Andasin IV traces his relationship to clan Kand.
Mirelael Irien, for her part, was also a member of a lesser branch of clan Kand and traced her relationship to the clan through her mother to her grandmother, Melise Kand.
Another example, not as well documented, brings us back home to Chybisa and clan Burzada. Trick question: What is the family name of King Gebral (ruled 590 to 627)?
If you answered "Burzada," you are probably wrong. His clan name (and apparently adopted family name) is Burzada, but that is not his birth name (father's family name). To uncover the facts behind that, we have to go back to Gebral's grandfather, Lonatar Burzada, and follow the line of succession.
In 559, the Red Death killed King Lonatar (ruled 541 to 559) and the Crown Prince, along with most of the royal family. That left Sabalyne, his fourth child and second daughter*, to inherit the crown. Sabalyne was crowned and married, probably in that order, and produced a number of children, one of whom (Gebral) would inherit the throne.
Now, since Sabalyne was the daughter of Lonatar Burzada, her maiden name was Burzada. Her husband, almost certainly, was not a Burzada, so the surname of their children is technically not Burzada. We see them carrying that name on the geneology chart but, again, that is an example of a family adopting (or retaining) the clan name as they inherit the clan's titles.
What is their actual family name? Well, it turns out that is up to you! There is no record of it anywhere I've seen and, until you flesh out the history, Sabalyne's consort remains a faceless, nameless noble. Chances are he has relatives somewhere...
*You have to dig back into the old 1st edition HârnDex to find this tidbit - look under the entry for "Sabalyne."
For starters, clan does not equal family. A clan is composed of a number of families. Some of these families will carry the clan name as a surname, but others will not.
Said another way, a kingdom that has, say, 300 unique surnames does not have 300 clans. How many will it have? That is up to you. As a reference point, note that some large Scottish clans include as many as 200 surnames; most have somewhere between one dozen and two dozen different surnames. With that as a guide, a kingdom that has 300 surnames might consist of 15 clans. Only a small number of these will be the great clans -- the ones who are tenants-in-chief of the king.
Coming Soon! Hârniac conventions regarding noble surnames vs the "of [surname]" used by commoners.