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.
Second cousins.
Biologically, the grandchild is a step-grandchild to the grandparent that had no children. In matters of the heart, however, the grandchild is whatever the grandparent feels it is.
Your great uncle's grandchild is your second cousin.
second cousin
If the daughter is biologically related to you, it would be your great-grandchild. If your husband had his daughter before he married you (which would make her your step-daughter), it would be your step-great-grandchild.
Your great grandmother's sister is your great great aunt. Her great grandchild is your third cousin.
If the step-dad has or shares custodial authority, he can prevent the child seeing grandparents for any reason.
He would be his great great great uncle
second cousins twice removed.
Well that would depend on if you were the biological grandfather. If so then the grandchild is also your grandchild. If the child was born to a child of your ex-wife and not fathered by you then they are no relation to you and you would call them by their name.
They would be your step-grandchild.
You and your first cousin's grandson are first cousins, twice removed, to each other.