by his given name of course.. or cousin
You would usually call the children of your husband's first cous by their name. They are not related to you. If you need to refer to them in a general sense, you might call them your husband's first cousins once removed.Yuor husband's first cousin's child is related to you children as a second cousin.
Your cousin-in-law.
In genealogy terms she would be "spouse of your first cousin."
Children of your siblings are nieces and nephews. Children of your spouse's siblings are still called nieces and nephews, but you are not related to them by blood.
The English language does not have a widely accepted relationship term for the husband of your first cousin. That person is not considered to be related to you. If you must describe him other than by name, you might call him your "cousin's husband." Some people use the recently invented term "cousin-in-law."
== NO she is not related to you. == No, she is not your cousin at all even though she's your husband's cousin. You are not blood relatives. If you like her you could put her down for a personal reference for a job, but other than that you don't have to mention her at all for a job.
Most students never call their first cousins and some don't event know who they are.
Your baby and your cousins are first cousins once removed to each other. You baby and your second cousins are second cousins once removed to each other.
TwiNs
The children of your first cousin are your first cousins, once removed.
You and your father's first cousin are first cousins, once removed.
Your First Cousin's child is your first cousin, once removed.