Your cousin's brother is also your cousin. His son is your first cousin once removed.
To work out the first cousin (or second or third cousin) part you have to work out which grandparents you share.
If you both share somebody as a grandfather or grandmother, you are first cousins.
If you both share the same person as a great-grandparent you are second cousins.
If you both share the same person as a great-great grandparent you are third cousins.
If it is unequal you start talking about "removed".
Like this question asks - your cousins brother son shares your grandparents with you, but for him they are great-grandparents. It is an uneven share. There is a difference of only 1 generation. So you are "once removed".
Your grandmother is first cousins with cousin. Your parent would be the second cousin of the cousin's son. That would make you second cousins once removed.
The daughter of your brother is your niece.
What is your great-great-great grand nephew?!
You and your mother's brother are first cousins. There is a generation difference between your son and the daughter. That makes them first cousins once removed.
Our cousins are our mothers sisters son :)
Step-brothers
Your cousin's son is your cousin, once removed, but it is probably best to call him or her by their first name.
cousin because your cousins son is your 2 cousin
Your aunt's son and your children are first cousins to each other.
Great great cousins.
Your uncle's sons and daughters are your first cousins.
Two people who have at least one grandparent in common are first cousins. Your son and your stepbrother's son may be first cousins, or may be unrelated. Even if they are unrelated that can call each other first cousins if they get on well together and want to do that.