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.
Second cousins.
Your uncle's child is your first cousin. His grandchild is your first cousin, once removed. You are also that grandchild's first cousin, once removed.
Your great uncle's grandchild is your second cousin.
Grandchild
Your daughter and your sister's child are first cousins. Your daughter and your sister's grandchild are first cousins, once removed.
second cousin
It means that they died on the day that a child or a grandchild was born.
You should be able to get your grandchild, because it is not good for the child to have no chance of finding friends and have a normal life, that is never something what a child should live, it is very important that you get your grandchild! Greets from Germany :)
Does the stepchild and your child share a parent? If so, they are half-brothers, which would make the grandchild your son's nephew.
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 grandchild