second cousins twice removed.
The grandchild of your grandmother's first cousin is your third cousin. The grandchild of your grandmother's second cousin is your fourth cousin. The grandchild of your grandmother's third cousin is your fifth cousin.
Your great uncle's grandchild is your second cousin.
second cousin
Your great grandfather's sister is your great great aunt. Her grandchild is your parent's second cousin and your second cousin, once removed.
Your father's first cousin's grandchild is your second cousin, once removed. Your father's second cousin's grandchild is your third cousin, once removed. Your father's third cousin's grandchild is your fourth cousin, once removed. And so forth.
Second cousins.
Your first cousin's child and your child are second cosins. Your first cousin's grandshild and your child are second cousins, once removed. Your second cousin's child and your child are third cousins. Your second cousin's grandchild and your child are third cousins, once removed.
Your second cousin, twice removed, is the grandchild of your second cousin (the great great grandchild of your great aunt or great uncle) or the second cousin of your grandparent.
The child of your parent's first cousin is your second cousin. The grandchild of your parent's first cousin in the child of your second cousin and thus your second cousin, once removed.If you are starting with your parent's second cousin, then the grandchild is your third cousin, once removed.
Your first cousin's grandchild is your first cousin, twice removed. Your second cousin's grandchild is your second cousin, twice removed. If you start looking a grandchild of a first cousin once removed, a third cousin twice removed, etc., the answer becomes more complex and depends on whether you are a member of teh younger or older generation in the relationship.
Thew brother of your mother's cousin is also your mother's cousin, and the same kind of cousins - first second, etc. So the question is really, "How are you related to you mother's cousin's granddaughter." Your mother's first cousin's grandchild is your second cousin, once removed.
Your uncle's grandchild would be your second cousin because his grown son or daughter would be your first cousin.