Explanation:

Let’s break it down:

- Primary kin: These are your direct blood relatives—parents, siblings, and children. Super close, direct lines only.

- Secondary kin: These are one step further—think uncle, aunt, nephew, niece, grandparents, and grandchildren. They're related, but there’s one person standing between you and them.

- Tertiary kin: Now we’re two steps removed. This is your dad’s cousin, your cousin’s children, or in this case, your father’s sister’s stepson. There’s a chain: you ? father ? father’s sister ? her stepson. Not a direct line, and not completely unrelated.

So, here’s the answer:

- Option 3: Tertiary kin is right—your father’s sister’s stepson is your tertiary kin.