Covid

Hey guys quick question abt covid.

Basically my boyfriends extended family already caught covid and healed over a month ago and now have the antibodies for it. They flew on a plane with three other friends who never had covid prior. These three ended up catching covid from the plane and went back home. My boyfriends extended family however didn’t catch anything from the plane and believed it was bc of the antibodies, and show no symptoms at all.

They’ve visited my boyfriend a few times and have stayed outside with masks (most of the time) except for eating, etc. he’s also going to take an at home antigen test so we could hang later this week. Is this safe though? Is it likely tht his ex trended family could have been carriers since they were exposed to it a second time but didn’t catch anything at all?

Please let me know