"B-but I thought family meant nothing to you Rick!" Morty's fists were trembling by his side, even as his eyes filled with frustrated, embarrassed tears and his face turned redder and redder.
"Y-you told Summer-"
"Yeah Morty, I did. I'm not going senile yet, I remember two weeks ago." Rick's bored response, still not looking up from his computer, was infuriating for Morty. All the dirty stories he'd read in the weird parts of the internet, coupled with his own imagination, seemed to lead to an incredibly anti-climactic rejection.
"W-w-w-well then, I don't know, aren't you at least shocked or something that I asked Rick? I mean, i-isn't this unexpected at least? Or something? Shouldn't, shouldn't you be, I don't know, shaming me or something?" He hollared desperately, flinging his arms up in the air, hoping to at least get something out of this huge risk and incredible embarrassment.
"Sorry to burst your bubble Morty, but I really couldn't care less about your pathetic fantasies. If I was gonna do some weird puritanical earth sex shaming, wouldn't I have done it when you bought that sex robot?"
"W-w-w-w"
"Oh god, I never did get around to that name you gave her though; jeez Morty, if there's anything to be embarrassed about, it's naming your sex robot "Gwendolyn." Ugh."
"W-well then, if you're not opposed to it or gonna shame me or think I'm disgusting-"
"-I always think you're disgusting Morty-"
"-then why are you turning me down?"
At this, Rick finally turned, one cheek pulled up in a look of boredom mixed with dubious disdain.
"M-morty are you seriously asking me why I don't want to have sex with you? You literally think the only things standing in the way are that you're underage and related to me? I-I-I mean, have you seen yourself, Morty? You're a scrawny little teen, Morty. You're desperately horny, needy, average little-li-little fucker. If anyone even remotely bangable even touched your little pants you'd prolly die from how hard you came. What coOOUUULd possibly be in it for me Morty? Do you know how easy it is for a Rick to get laid Morty? Sheesh. Go back to your internet porn, and stop searching "nude selfie" on my computer when I'm gone Morty, you're not sneaky."
Mortified, Morty turned to walk to his room.
It never really occurred to him that Rick, even if it wasn't already established in canon that he wasn't into incest, just wouldn't be attracted to him.
The end.