Oh no, he didn't! Kylie Jenner is apparently livid over boyfriend Tyga's congratulations message to his ex-fiancée Blac Chyna, 27, and Kylie's half-brother Rob Kardashian, 29, on their engagement.

So much so, reports Radar Online, that the here-and-there couple may be … there again.

Rob proposed to Blac (the mother of Tyga's son King Cairo, 3) last week while his entire family was out of town on a ski trip. The Kardashians have stayed uncharacteristically mum on the news, with a few exceptions, including Kim Kardashian's husband Kanye West and Kylie's guy.

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Kylie Jenner and Tyga with King Cairo.

"It makes me happy to see the mother of my son happy," Tyga tweeted before launching into a cautionary diatribe about how his biggest concern is for his son.

Since then, Kylie, 18, ditched her 26-year-old rapper beau at an LA premiere for his movie Barbershop and he jetted off on tour without her. So are these two broken up — again?

"Kylie had specifically told him to NOT say anything about it until she did," an insider revealed to Radar. "Tyga talked so much sh-t about Blac being with Rob to Kylie behind Blac's back and to everyone else, and then he goes and sends them well wishes. It just really pissed her off!"

RELATED: Are Rob Kardashian and Blac Chyna Already Talking Babies?

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Rob Kardashian and Blac Chyna.

The biggest upset for the youngest Kardashian sister, though, stems from pure envy.

"Tyga knew that Kylie has wanted him to propose to her for so long now," the source said. "And now she is just legit jealous of her brother Rob and Blac’s upcoming wedding because the whole family is going to be focusing on that and not on her!"

Yeesh. Kylie, we feel you. But hang in there. You're only 18! Best not to rush into anything anyway.