The fact that he isn't trying to joke this away completely is at least partially due to Rey. She's convinced him that there is a need to talk about these things sometimes.

Is that an invitation for a lecture on Firo's favorite topic? No? Too bad. Firo bats her arm in return. Despite the playful gesture, his face is completely serious. "They are supposed to. That's what makes it family--you look out for each other and help each other out when you need it. Somebody who wouldn't do that doesn't deserve to be considered your family at all."