My great-grandma
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.
Your mother's brother is your uncle.The children of your aunts and uncles are your 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 third cousins are your fourth cousins. And so forth.
Your mother's sister's children are your 1st cousins.
Your mother's nieces' children are your mother's grand nephews or grand nieces. They are 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 sister's children, sons or daughters, are your first cousins. The children of first cousins are second cousins to each other. That is the relationship between your children, or either sex, and your first cousin's children, of either sex..
Relationship sequence:Your uncle is your mother's brotherHis children are your first cousinsHis grandchildren are your first cousins once removed
The common ancestor is your parents. Your children and your sister's children are first cousins. Your grandchildren and your sister's grandchildren are second cousins. Your great-grandchildren and your sister's great-grandchildren are third cousins.
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.
They are 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.