There is no relation that is properly called a step cousin.
If you like your cousins girlfriends kid then i think its okay since its not your cousin but you may want to discuss it with your cousin and his girlfriend first.
You are cousins by marriage.
Nothing because it is your step father and his cousin If your stepfather were in fact your father, the son of his First Cousin would be your Second Cousin. If you are close to your stepfather, or were formally adopted by him, you might call that person your Step-Second Cousin. If you really like your stepfather, or his cousin's son, and want to assert a relationship, you could even call him your Second Cousin.
The grandchild of your grandmother's first cousin is your third cousin. The grandchild of your grandmother's second cousin is your fourth cousin. The grandchild of your grandmother's third cousin is your fifth cousin.
Your cousin's child would be your cousin once removed. So your cousin's stepchild would be your step-cousin once removed.
Cousin. Your parents brothers and sisters are aunts and uncles. and the aunt and uncles children are your cousins.
Well I've heard that a 'step cousin' is a step parent's nephews and nieces. Meaning if your father and mother got a divorice, your mother remarried to a man who is now your 'step dad' then his brother or sister's children are your 'step cousins'. Also, I believe to use it with my other 'cousin'. I believe step father or mother means a father or mother because of marriage, not a blood parent. So, I believe that when my aunt married my uncle, my uncle became my 'step uncle' or 'uncle by marriage' and his brother's or sister's children are now my 'step cousins' or 'cousins by marriage'. This may be incorrect but that is how I choose to describe my aunt's husband's brother/sister's kids. I like to be able to call them my cousins because I am so close to them!
Your half second cousin's son would be your second cousin once removed.
There is no relationship of "quarter cousin." If you have a first cousin, your son and that first cousin are first cousins, once removed. If you have a second cousin, your son and the second cousin are second cousins, once removed. Whatever cousin you have, your son and that cousin are the same kind of cousins, once removed.
for female cousins : cousine for male cousins : cousin
All of your cousins are also cousins of your brother.