Shailene Woodley and Aaron Rodgers have a "non-traditional relationship"

A source explained: "They have a different, non-traditional relationship."

Aaron celebrated his latest birthday on December 2, and was seen out and about without his girlfriend.

However, that Shailene didn't acknowledge the occasion on social media doesn't mean anything, according to the source.

The insider told People: "Shailene and Aaron are still together. It's not odd they don't post about each other on their birthdays in that sense, and are very private about things."

Aaron - who previously dated actress Olivia Munn - recently signed a new deal with the Green Bay Packers in the NFL, and he stressed the importance of having good communication in his personal and professional life.

The sports star admitted it takes time and patience to build a successful romance.

He said: "Relationships aren't formed in a matter of a couple days.

"There's time where the respect grows and the communication follows. I think the greatest relationships that you have with your friends and loved ones involved conversation and flow. You can not talk to a close friend for a few months and pick up right where you left off. There's no break in communication, there's no forced conversations or you've got to hit this person up because it's on your to-do list that day."

Meanwhile, Shailene previously admitted she never watched an NFL game before she started dating Aaron.

The Hollywood star explained that the Packers games "are the only ones I find really interesting because I have people to actually root for".

Speaking about her new passion, Shailene said: "It is a whole new world, learning all of the different - I still am always, 'Oh, you scored a goal.' He's like, 'It's a touchdown.' Or I'll be like, 'You crossed the line,' and he's like, 'It's a yard,' or whatever."