Yes, your husband is considered to be your closest relative.
Before or after a divorce a step-sister is not considered a legal relative in most jurisdictions.
If you have a girlfriend and a boyfriend, then you are cheating on both of them.
SHe's your relative by virtue of her sister being married to your brother.
His relative and boyfriend Patroclus.
If by "stepson" you mean someone who was legally adopted into the family - yes, they are a legal relative. However, they are NOT considered to be a "blood" relative.
Depend on how long they have been dating
When he calls you his girlfriend.
NO
Only if the court determines it would be in the best interests of the child to award such custody. The biological parents and/or an immediate relative of either would be considered before a person with no legal or biological ties to the child.
Yes, your wife is a relative by marriage, and is considered to be your closest relative.
Yes, she is your sister-in-law.