Random corner-case trivia note here, but I was fairly certain this wouldn't work when I first set out to try...
- My husband and I have a JetBlue family pool.
- He has Mosaic status, I do not.
- I have a JetBlue credit card, he does not.
- As one of the perks of the JetBlue Master Card, I get a $100 discount on a companion fare.
- But since he's Mosaic and we love the 800-point upgrades to Even More Space, we usually try to book under his account when we travel together
I'm pleased to report that my companion discount worked just fine when we logged in and booked the tickets from his account. So yes, other people in your JetBlue family pool can use your JetBlue Master Card companion discount.