Your first cousin's uncle is either your father, one of his brothers or one of your mother's brothers, or is not related to you (an uncle through the spouse of your father's sibling).
The uncle's mother is either your grandmother or someone not related to you because she is on the other side of the cousin's family.
It does, of course, happen that people marry their 1st cousins or 2nd cousins in which case both of your cousin's grandparents would be related to you. Ancient Egyptian royalty used to marry their own brothers and sisters, which made working out their ancestry very easy.
Anyone descended from a brother or sister of one of your direct ancestors is your cousin. There are different names for different kinds of cousins. For example, your first cousins are the children of your aunts and uncles. Your second cousins are the grandchildren of your great aunts and great uncles. Your parents'first cousins are your first cousins, once removed. And the children of your first cousins are also your first cousins, once removed.
Let's approach this systematically. Your mother's and father's parents are your grandparents. Your mother's and father's siblings are your aunts and uncles and their children are your first cousins. The children of your first cousins are your first cousins ONCE REMOVED (thereby establishing both the relationship and generational standing) The siblings of your Grandparents are your great aunts and great uncles. Their children are your parent's first cousins. Therefore your great aunt's niece is your first cousin, once removed, or she may be your mother.
Your mother's brother is your uncle.The children of your aunts and uncles are your first cousins.
The cousins of your in-laws are not related to you and neither are their parents. However, the parents of your spouse's first cousins are your spouse's aunts and uncles, and thus your children's great aunts and great uncles.
Your aunt is the sister of either your father or your mother. If your aunt is your father's sister, then your father's cousin is also her cousin. If your aunt is your mother's sister, then she is not related to your father's cousin.
The grandchildren would be the parents, aunts and uncles, and first cousins once removed, of the great grandchildren.
Sam and his mother's sister's son are first cousins, just as you and Sam are first cousins. But you are not related to Sam's mother's sister's son.
The children of your mother's first cousins are your second cousins. The children of your mother's second cousins are your third cousins. The children of your mother's third cousins are your fourth cousins. And so forth.
You are related to some of your cousin's cousins, and not to others. If you have an ancestor in common, you are related. If you do not can a common ancestor somewhere, then you are not related.
they were first cousins
The children of your mother's first cousins are your second cousins. The children of your mother's second cousins are your third cousins.
The children of your mother's first cousins are your second cousins. The children of your mother's second cousins are your third cousins. And so forth.