What is my son-in-law's mother to me?
Your son-in-law's mother is your co-mother-in-law. English never adopted a native word for your child's spouse's parents — many languages did (Spanish has 'consuegros,' Yiddish 'machatunim') — so genealogy borrows the 'co-' form. You are joined by your children's marriage, and share grandchildren, but not a drop of blood.
Relationship
Co-mother-in-law
English has no single formal word for this relative — “co-mother-in-law” is the label genealogists use.
- You
- Your son-in-law
- His mother
From the other side, you are their co-parent-in-law.
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
What are my son-in-law's parents to me collectively?+
Your co-parents-in-law — the two sets of parents of a married couple are co-parents-in-law to each other.
Who am I to my son-in-law's mother?+
Her co-parent-in-law — the relationship is symmetric.
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.
