Second-cousin-once-removed.
I don't know my 2C1R.
My 2C1R is a good person.
1- Second-cousin-once-removed's spouse. 2- Spouse's second-cousin-once-removed.
My 2C1R-in-law is a good person.
Spouse's second-cousin-once-removed's spouse.
My co-2C1R-in-law is a good person.