Your parent's first cousins are your "first cousins once removed". When referring to cousins, the number indicates (first, second etc) indicates the number of generations since you had a common ancestor. For first cousins the common ancestor was two generations previous (i.e grandparents), for second cousins it was three generations and so on This only works if the cousins are in the same generation. Therefore the 'removed' indicates the number of generations separating the people concerned. When you were born, you were one generation removed from your parents first cousins i.e you were their 'first cousin once removed'. The child of your parents cousins are your second cousins. It may be easier to understand this with diagrams rather than with words.
Your child and your great nephew's parents would be first cousins. Their children would then be second cousins. And if they have children, they will be third cousins.
Your niece and one of your grandson's parents are first cousins. That makes your niece a first cousin once removed of your grandson.
If two people have grandparents who were siblings, then their parents are first cousins and they are second cousins.People whose grandparents are siblings are second cousins.
You are never a member of the same generation as your grandparents or your parents. Your generation is the one that includes you, your siblings, and your first cousins, second cousins, etc.
If two people are first cousins, the children of one are second cousins to the children of the other.
The children of your parent's first cousins are your second cousins. The children of your parent's second cousins are your third cousins.
Your child and your great nephew's parents would be first cousins. Their children would then be second cousins. And if they have children, they will be third cousins.
Anyone who has a great grandparent in common will be second cousins. Another way to look at this is to note that the grandchildren of your great aunts and great uncles are your second cousins. Their children are your second cousins, once removed, and their parents are your first cousins once removed.
Your third cousins are those relatives who share a great-great-grandparent with you. They are the children of your parents' second cousins and the grand children of your grandparents' first cousins.
If you and another person have parents who are first cousins, then you and that other person are second cousins, because you have a great-grandparent in common.
They would be second cousins. Your child and your grandniece's parent are first cousins. There are no 'removed' involved because the generation difference between the common ancestors (your parents) is the same.
Your niece and one of your grandson's parents are first cousins. That makes your niece a first cousin once removed of your grandson.
Your first cousins childrens are your second cousins.
The children of your grandmother's brother (of your great uncle) are your parents first cousins and your first cousins, once removed. The grandchildren of your great uncle are your second cousins.
If two people have grandparents who were siblings, then their parents are first cousins and they are second cousins.People whose grandparents are siblings are second 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 parent's first cousin's children are your second cousins. Your children and your second cousin's children are third cousins. Your children and your second cousin - or likewise you and the children of your second cousin - are second cousins, once removed. You and your parent's first cousin are first cousins, once removed.