My brother-in-law and my mother-in-law are very friendly.
Cam I rephrase the sentence as follows?
My brother- and mother-in-law are very friendly.
I understood your written thread title perfectly, Tan Elaine, but in speech you can't hear the first hyphen.
I'd write it out in full as bhai recommends.
In case you care, in writing, it's called the suspended hyphen.
But hey, you could always say "My husband's brother and mom are very friendly."
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.