uncle
brother
You're not related.
granduncle - grandnephews/grandnieces
None. There is no relation through "my friend"
They are half brother and sister, they have the same father but different mothers.
the relation is that person is either your half brother or half sister. 1/2 brother or sisiter
Your mothers sister is your Aunt
No relation
It depends on who you are in relation to these people, what items you are asking about, and what you mean by "rent book".
Your relation to your mums uncle is GREAT uncle. You're welcome! 
Mothers brother ( uncle ) = amoo
Brother-in-law