Your uncle is the brother of your father or mother.
Your aunt is the sister of your father or mother.
Your great uncle (or grand uncle) is the brother of your grandfather or grandmother.
Your great aunt is the sister of your grandfather or grandmother.
Your great-great uncle is the brother of your great-grandfather or great- grandmother.
Your great-great aunt is the sister of your great-grandfather or great- grandmother.
Your first cousin is the child of your aunt or uncle.
Your second cousin is the grandchild of your great aunt or great uncle. (If two people are first cousins, the children of each of the people will be second cousins.)
Your third cousin is the great-grandchild of your great-great uncle or great-great aunt. (Children of 2nd cousins, are 3rd cousins to each other.)
Your first cousin, once removed, is the child of your first cousin or is the child of your great uncle or great aunt.
If someone is your first cousin, then his or her child is your first cousin once removed. (Once removed means one generation level different from you.) All your regular cousins (first, second, etc.) are at the same generation level as yourself. Those at different levels are "removed." If someone is YOUR first cousin once removed, then you are HIS or HER first cousin once removed also. Your second cousin once removed is the child of your second cousin. Your first cousin twice removed is the child of your first cousin once removed (i.e. the grandchild of your first cousin). Your second cousin twice removed is the child of your second cousin once removed (i.e. the grandchild of your second cousin).
REMOVED COUSINS: If two people are some type of cousins, but they are at different generation levels, then here is the way to compute their relationship.
Count how many generation levels they are apart. This is the number they are "removed."
Start with the one at the highest generation level (the older level) and count how many generations up you must go to find the brothers or sisters that are the ancestors of these cousins. This is the "FIRST" or "SECOND" or "THIRD" part of the cousin relationship.