Tyga has become very bold with his Instagram posts now that Kylie Jenner is of age.

The Keeping Up With the Kardashians star turned 18 on Monday, and in honor of her big day, the 25-year-old rapper posted what could be the sexiest photo of Kylie we've ever seen.

WATCH: Khloe Kardashian Hugs It Out With Kylie Jenner and Tyga

"Happy bday to dopest girl ever," he captioned the sultry image of his rumored girlfriend.

Is this his way of telling us he's officially with the reality star?

Tyga also fueled romance rumors when he purchased Kylie a Ferrari for her birthday!

Tyga nor Kylie have confirmed their relationship but big sis Khloe Kardashian addressed the speculation in her interview with Complex magazine.

"I think at 16 I was probably f**king someone that was in their 20s, for sure," Khloe confessed. "I wouldn't say I was even dating, probably just sleeping with them."

WATCH: Kim Kardashian Looks Identical to Kylie and Kendall Jenner in Shocking Split Pics

Commenting on how young her sister is, Khloe insisted that she's not your typical teenager.

"You're not gonna say, 'Hey, so what are you doing this weekend?' and have her say, 'Having a slumber party at my girlfriend's,' or 'Going to prom.' That's not what Kylie does," she said. "Kylie is taking business meetings and bought her first house, or she’s going on a private plane with Karl Lagerfeld to take a meeting. That's not even what people do in their 30s. It's a rare circumstance, so let’s treat this as a special case."

NEWS: Kylie Jenner Squashes Rumors She's Marrying Tyga

Over the weekend, Kylie kicked off her birthday celebration with a family dinner at Los Angeles' Nobu. Obviously, selfies were taken.

All five sisters were at the dinner along with both Cailtyn and Kris Jenner, which marks the first time Kylie's parents have been seen in public together since Caitlyn announced she was transgender. Her brother, Rob, however, was the only one of the Kardashian clan that wasn't spotted at the get-together.

Kylie is constantly having to address rumors about her personal life, including recent reports claiming she's planning on getting married: 

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