What is my brother-in-law's daughter to me?
Usually your niece by marriage. If your brother-in-law is your sister's husband, his daughter with her is simply your niece by blood. If he's your spouse's brother, his daughter is your spouse's niece — your niece by marriage, which everyday speech shortens to plain 'niece' anyway. Only the paperwork distinguishes the two.
Relationship
Niece by marriage
English has no single formal word for this relative — “niece by marriage” is the label genealogists use.
- You
- Your brother-in-law
- His daughter
From the other side, you are their aunt or uncle by marriage.
This connection runs through a marriage, not a shared ancestor, so the ancestor chart can't draw it.
The calculator below works out blood relationships through a shared ancestor — use it to explore the rest of your tree.
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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.
FAQs
Is my brother-in-law's daughter my niece?+
In everyday speech, yes. Genealogically it depends on whether the brother-in-law married your sibling (blood niece) or is your spouse's sibling (niece by marriage).
Who am I to my brother-in-law's daughter?+
Their aunt or uncle by marriage — or a blood aunt or uncle when the link runs through your own sibling.
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.
