I want to know how to call few relations like: my
brother-in-law's sister
brother-in-law's sister's son/daughter
sister-in-law's brother
sister-in-law's brother's son/daughter
I want to know how to call few relations like: my
brother-in-law's sister
brother-in-law's sister's son/daughter
sister-in-law's brother
sister-in-law's brother's son/daughter
I just consulted my mentor whom is studying in the Ministry of Education in Singapore.
Brother-in-law's sister is basically sister-in-law. That's the shortest. For their son or daughter, either distant cousins or cousins-in-law, but I would not parse the latter.
brother-in-law's sister
Sister-in-law
brother-in-law's sister's son/daughter
Sister-in-law's son/daughter
sister-in-law's brother
Brother-in-law
sister-in-law's brother's son/daughter
Brother-in-law's son/daughter.
But mostly we just call them the animals that run around screaming, and knocking stuff over while their good-for-nothing parents drink our beer and laugh at their antics.