Demi Lovato and Wilmer Valderrama's strong relationship is first and foremost based on a "beautiful" friendship.
ET caught up with Wilmer at Jennifer Lopez's first show of her Las Vegas residency at Planet Hollywood Resort and Casino's The AXIS on Wednesday night, when he dished on the secret to their longtime courtship.
"You know, we've been best friends for about six years," Wilmer, 35, said. "We haven't necessarily been dating for six years, but we have six years of friendship, and it's been... it's been beautiful."
WATCH: Demi Lovato Flaunts Her Swimsuit Bod, Makes Out With Wilmer Valderrama
"All I did was love her exactly when she needed me to love her," he added. "And you know, we just stay honest. That's it."
Cue the Awwwws!
Wilmer was clearly enjoying a guys' night out on Wednesday at Lopez's after-party, sticking close to the singer's good friend and The Boy Next Door co-star, 28-year-old Ryan Guzman. A bearded Guzman flew out just for the night to support Lopez.
When ET caught up with 23-year-old Demi last week, she also clarified that the two were friends first before becoming romantic. The "Confident" singer has previously said the two started dating when she turned 18.
"Everyone thinks it's our six-year anniversary. We met six years ago!" Demi explained about an Instagram pic she shared last week of the two cuddling, with the caption "6."
"He had some hesitations [initially]," Demi also admitted about their 12-year age difference. "Once I got older, we could be together. He's my best friend."
WATCH: EXCLUSIVE -- Demi Lovato Reveals Wilmer Valderrama Had 'Some Hesitations' About Their Age Difference
... So could 2016 be the year Wilmer puts a ring on it?
We already know she would definitely say yes!
"You gotta ask him!" Demi told ET last month at Billboard's 10th Annual Women in Music event in New York City. "I have no idea."
Watch the cute response below.