This is really creeping us out ... could 17 year-old Kylie Jenner be dating Tyga -- the 24 year-old rapper and former fiance of Kim Kardashian's BFF Blac Chyna??? Talk about friends sharing everything!

Our photographers spotted Tyga out at Katsuya Hollywood Tuesday night and apparently all the paparazzi outside were buzzing about the fact that he was dining with Kylie. Now, OK! magazine reports a source is telling them: "Kylie always had a crush on him; but as she got older and they started spending more time together, things took off romantically." Dang!

Tyga took to Twitter to deny the report, writing: "DONT BELIEVE THE RUMORS, BEEN FRIENDS WITH THE FAMILY FOREVER. WERE ALL JUST FRIENDS. [sic]. Rumors come and go. But you keep your shadow. Everywhere you go it follows."

Tyga split from fiancee Blac Chyna in August; the pair have a two year-old son King Cairo and had been dating for almost three years. The couple lived together in the same neighborhood as Kris Jenner -- hence Kim's frequent gym and salon trips with her fellow big-booty'd pal Chyna.

Kylie previously dated Will Smith's son Jaden -- though the two never confirmed their relationship. Before that, she was with teen heartthrob Cody Smith. She and sis Kendall have been known to party with Tyga and his friend Chris Brown -- as they did on Kylie's 17th birthday last month and at the opening of Tyga's clothing store Last Kings in February (below).

You think Tyga's the right guy for Kylie???