If i am not wrong there was actually a Rana constitution or Shah constitution that dictated how Jaat were dropped if married outside of the clan.

Thakuris the royals - these could mary anyone and never dropped their casts, The real chetris like thapa, basnet, and such....and then bigreko bahun haru chetri lol ( same last name as the chetris but were dropped for marrying another cast...very hillarious if you really think about all these variations.

Now someone with the last name of Bhujel explained this to me.

Here are the derivatives of Bahuns and Chetries.

Pure Upadhhe bahun - the one who can perform karma kanda
Kumai Bahun - Bahun who is also a bahun but will not perform karma kanda
Jaisi bahun - Derivative of upadhhe bahun, father married a widow or eloped a wife without kanyadaan. Bahun who did not follow all the bahun rules.

Chetri - Offspring of Bahun and lower
Khatri Chetri KC - Offspring Chetri and lower
Gharti chetri GC - Offspring of KC and lower
Bhujel - Offspring of GC and lower

( all of the bahun and chetri derivatives are then grouped with GOTRA - same GOTRA is another big NO NO for marriages, if that complexity was not enough for you : ) ( interesting and hillarious) at the same time.


then there are other pure bred janajati like gurung, magars, tharus, newars,,,,i do not know the derivatives of these.