Your mother's brother is your uncle. You are his niece (if you are femlae) or his nephew (if you are male).
brother
uncle
You're not related.
granduncle - grandnephews/grandnieces
None. There is no relation through "my friend"
They are brothers in law
They are half brother and sister, they have the same father but different mothers.
relation between kaikeyi and pandavas
the relation is that person is either your half brother or half sister. 1/2 brother or sisiter
she would be your sister in law
They were brother and sister.
No. There is no relation between Zexion and Riku.