What is my son's mother-in-law to me?
Your son's mother-in-law is your co-mother-in-law. She is the mother of the person your son married, which puts the two of you on opposite sides of one marriage. English never settled on an everyday word (Spanish says consuegra), so most families use her name. You share no blood, though any grandchildren belong to you both.
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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
- His spouse
- Their 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.
Related questions
FAQs
Is my son's mother-in-law the same as my daughter-in-law's mother?+
Yes. Your son's spouse is your daughter-in-law, so their mother is your co-mother-in-law either way you ask.
Who am I to my son's mother-in-law?+
Her co-parent-in-law. The word works the same from both sides.
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.
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