If you are female and have a son, your aunt's niece's son could be you.
Your aunt's niece's son could also be your first cousin, once removed, if he is the son of one of your first cousins.
Your aunt also may have nieces who are not related to you, and then the son is not related to you either.
Your granddaughters and son have the relationship of nieces and uncle. Your granddaughters being his nieces and your son being their uncle.
First cousins, twice removed. Aunts daughter is your cousin. Aunts daughters daughter is cousin once removed Aunts daughters daughters daughter is cousin twice removed.
Your mother's aunt's son is her first cousin and your first cousin, once removed.
They would be 3rd cousins.Grandma-GrandpaMom-Auntyou-cousinson-3nd cousinthe diagram is supposed to show that if your cousin has a baby it would be your son's 3rd cousin because your cousin would be his 2nd cousin.
A nephew is a cousin to his aunt's son.
Your son and your aunt's child are first cousins, so your son and your aunts grandson (the son of your aunt's child) are first cousins, once removed.
Assuming he is your only sibling with female children, you would have two (2) nieces.
In-laws are not related.
If her son is from a previous relationship, then he would be your step-son.
Your uncle is either the brother of your mother or father, or the husband of a sister of your mother or father. If your uncle is a brother of your mother, then his sister's son is you (if you are a boy) or your brother, or your first cousin (if the son is the son of another sister than your mother). If the uncle is a brother of your father, then his sister is your father's sister (your aunt) and her son is your first cousin. If the uncle is husband of the sister of your mother or your father, then the sister's son is not related to you.
Second Cousin
Your niece's son is your grand nephew, and you are his great aunt.