Your cousin's brother is also your cousin.
His child is your cousin once removed. For example, if your first cousin has a child, that child is your first cousin, once removed. If your third cousin has a child, the child is your third cousin, once removed.
The daughter of your brother is your niece.
Cousins
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
cousins
Your aunt's son and your children are first cousins to each other.
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.
Nephew...
Your son and your niece are first cousins. Your son and your niece's son are first cousins, once removed. Your grandson, or granddaughter, and your niece's son are second cousins.