5SOS' Luke Hemmings Is Engaged to Girlfriend Sierra Deaton: 'I Can't Imagine My Life Without You'

Ryan Fleming and KayKay Blaisdell

Starting the summer with lots of love!

On Tuesday, 5 Seconds of Summer's Luke Hemmings shared that he proposed to his longtime girlfriend Sierra Deaton earlier this year as he shared photos of the special moment on Instagram. Hemmings asked the big question in an intimate setting in Malibu, California back in February, a source tells PEOPLE.

"With shaking hands but a full heart I proposed to my best friend earlier this year," the guitarist, 24, wrote. "I love you Thao and I can't imagine my life without you ❤️ @sierradeaton."

In one photo posted, Hemmings can be seen putting the large diamond ring on her finger as the two smile and look into each other's eyes. In another, the couple shares a kiss in front of a mountainous backdrop.

Ryan Fleming and KayKay Blaisdell

RELATED: The Celebrity Engagements of 2021

Deaton - who Hemmings started dating in February 2018 - shared a sweet message of her own with a carousel of photoS.

"It was fun keeping this a secret for so long, but my heart is nearly bursting at the seams. can't wait for forever 🤍 @lukehemmings," the 30-year-old wrote.

Deaton is a musician herself and competed on the third and final season of X-Factor US when she was in the duo Alex & Sierra alongside ex-boyfriend Alex Kinsey. Deaton later released music under stage name Essy and has provided background vocals for the band.

Ryan Fleming and KayKay Blaisdell

RELATED: 5SOS' Ashton Irwin Announces First-Ever Solo Project: 'I'm Ridiculously Excited to Share This'

Earlier this month, Hemmings shared a sweet Pride Month post for Deaton who is bisexual.

"There is still so much work to be done but wanted to wish everyone a happy pride," Hemmings wrote on his Instagram Story. "Especially to my beautiful bisexual biracial angel."

Last year, Hemmings revealed that he wrote 5SOS' track "Not In the Same Way" about his girlfriend.

"Well, it's about me and my current girlfriend, and she's incredible. Maybe Ashton was there as well, maybe he was writing about someone else, but that's where I was writing about from," he told Paper Magazine last year. "She's a beautiful human. It could be painted in such a... when the worst moments are written on paper, it doesn't look very good. It was very important that it was the other side of it, because a lot of the mistakes are mine, you know?"