My brother and I are BFF for this reason: everything he says and does comes off as light-hearted, as a joke, as something not to be taken seriously but he is, in fact, sincerely, genuinely, earnestly looking to be taken seriously. Everything I say and do comes off as sincere, genuine, and quite grave when, in actuality, I don't mean any of it to be taken seriously on any level. I'll push past his bullshit-eating grin and make him talk about what's bugging him, and he'll laugh both at me and with me. We make a good team.