For one individual to be a "blood cousin" to another individual their MUST BE a common ancestor. If not then they are not cousins by blood.
Some people call each other cousins by marriage. A "by marriage" cousin would then have some family unit incommon. I'm not sure if FTM would note "by marriage" cousins.
Some people call each other cousins by marriage. A "by marriage" cousin would then have some family unit incommon. I'm not sure if FTM would note "by marriage" cousins.