[...He doeeeeees feel a pang of possessive jealousy over Rex's new warden, when you say that...]

I don't recall him.

[Pauuuuuse, then, because that doesn't seem good enough:]

And anyway, whatever the hell it was happened in the first place? To make us like each other? It's pretty clear I screwed that over when I left! I mean, jeeze, how many people does he need ditching him? And even if I did remember him, where do I get off expecting him to ignore the fact that now, I'm just another asshole who hit the road when he needed them?

[How much of this is very faint memories about Rex, and how much is Harper talking about recently ditching his cousin on earth... is open to debate, but, yeah, he sounds a little stressed.]