What is my sister's boyfriend to me?
Your sister's boyfriend has no kinship term: English only hands out in-law titles at a wedding. Most people say "my sister's boyfriend" or use his name. If they marry, he becomes your brother-in-law, and some families start saying "future brother-in-law" once there's an engagement.
Want the same answer for your own family? Put the relatives you know into a free AncestorIQ tree, then ask how any two of them are related.
Start your tree, freeRelationship
Sister's boyfriend
English has no word for this person until there's a wedding. Families just say “sister's boyfriend”.
- You
- Your sister
- Her boyfriend
From the other side, you are their girlfriend's sibling.
A partner who hasn't married into the family has no family link for the ancestor chart to draw.
The calculator below works out blood relationships through a shared ancestor — use it to explore the rest of your tree.
Loading tool…
This relationship sits outside the shared-ancestor model, so the card above carries the answer and the calculator opens in its default state. Work out any blood relationship with it, or open the full relationship calculator.
Related questions
FAQs
Is my sister's boyfriend my brother-in-law?+
Not yet. The title comes with the wedding. Some families use "future brother-in-law" once there's a ring.
Who am I to my sister's boyfriend?+
His girlfriend's sibling, which has no title either.
Does the calculator store my family details?+
No — it runs entirely in your browser. Nothing you enter is uploaded or saved on our servers.
Start with one relative and see what comes back.
Add what you remember and AncestorIQ searches for the rest. Free to build your tree for as long as you like.
No credit card needed. Your tree stays yours.
