Definitions by OneEyedWilvis

co-uncle 

Your brother's or sister's brother-in-law, or your niece's or nephew's other uncle(s) that aren't your brothers.

Jonathon and I aren't blood related, as his sister married my brother, but we are co-uncles to Jack and Caroline.

co-uncle by OneEyedWilvis January 20, 2009

co-aunt 

Your brother's or sister's sister-in-law, or your niece's or nephew's other aunts that aren't your sisters.

Liz and I aren't blood related, as her sister married my brother, but we are co-aunts to the same children.

co-aunt by OneEyedWilvis January 20, 2009