You would have a variety of different relationships to the cousins of your first cousins. Some of them are you and your siblings, and some of them are also your first cousins. Second cousins of your first cousins may also be your second cousins.
In addition, your first cousins will have many cousins who are not related to you at all. You are lreated to your first cousins because each of you have one paret who is a sibling of one parent of the other. But each of you also has one other parent, who also has siblings and the children of those siblings are cousins to one of you but not to both.
They would be considered your 2nd cousins.
Your first cousins childrens are your second cousins.
They are not considered first cousins, unless your brother adopts them. If he did, they would be considered siblings and could not marry. Otherwise there is no legal relationship between them. They do not share a common ancestor.
Your father's first cousins are your first cousins, once removed.
First cousins can marry in many places because they are considered to have a close enough blood relationship that potential genetic risks or abnormalities can be assessed before marriage. However, second cousins have a more distant blood relationship, and the risk of genetic disorders decreases significantly, which is why they are generally allowed to marry.
Your grandmother's sister is your great aunt. Your great aunt's daughter is your first cousin, once removed.
Your Father's first cousins are also your first cousins, once removed.
second cousins or first cousins once removed
Hi, Ciara and T.i are cousins, full blood first cousins. Hi, Ciara and T.i are cousins, full blood first cousins.
Your uncle's first cousins are also your parent's first cousins and so are your first cousins once removed. Similarly his second cousins are your second cousins once removed.
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.
If two people are first cousins, their children are second cousins. If two people are fifth cousins, their children are sixth cousins.