Second cousins are people with whom you share a great-grandparent but not a grandparent.
"Step-Cousin" is not a "real" relationship term, but probably is used to mean a person who would be a cousin if you were the child of your parent's second spouse, when in fact you are the child of the first spouse, or viceversa. In that sense, you could have a step first cousin, step second cousin, etc. But they are not real cousins because you do not share any ancestor with them.
To add a little more clarity, "cousin" technically implies a blood relationship through at least one common ancestor. If you shared at least one grandparent with someone, one of each of your parents would be siblings to each other and you would be cousins. "Step" is a term referring to relationships that are created when an adult "steps" into an existing family as a new parent to kids who were born of a previous relationship. There is no blood connection but the relationship is not necessarily any less "real," valid, or worthwhile.
No. Step cousins are not related to anyone in your family, other than perhaps your step-siblings or step-parent.
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.
They would be third cousins.
You are cousins by marriage.
They are second cousins
Yes, second cousins are always related. Being second cousins means that you are the grandchildren of two people who were siblings (brothers or sisters). Marriage and divorce has nothing to do with it.
You and your second cousin's children are second cousins, once removed. Your children and your second cousin's children are third cousins.
They were cousins, perhaps second cousins.
Yes, they are step cousins.
She has no relationship with your step-daughter. They do not share a common ancestor. If you adopt her, they would become second cousins once removed.
If your father and your girlfriend's father are second cousins, then you and your girlfriend are third cousins. You share one or two great-great-grandparents.
You and your mother's second cousin are second cousins, once removed.