Justin Bieber "can't live without" Hailey Baldwin.

Hailey Baldwin

Hailey Baldwin

The 24-year-old singer proposed to the 21-year-old model during a trip to the Bahamas shortly after they rekindled their romance, and a source close to the couple has revealed that Justin is besotted with the blonde beauty.

The insider shared: "Ever since they reunited, they have been inseparable and Justin knows he can't live without Hailey.

"Justin and Hailey had talked about marriage before but Hailey didn't think it would happen so quickly."

The high-profile duo only rekindled their romance a few weeks ago, but Justin hasn't wasted any time in popping the question to the American model.

The 'Sorry' hitmaker - who previously dated Selena Gomez - reportedly considers his bond with Hailey to be "incomparable" to anything he's ever experienced.

The insider told E! News: "Justin made arrangements for the ring when they were in NYC and knew that he wanted to propose to her. It was a sudden decision but Justin always knew Hailey and him had a special bond that was incomparable."

Hailey - who is the daughter of actor Stephen Baldwin - is said to have been shocked by Justin's proposal.

But she still had no hesitation in saying yes.

The source added: "The proposal was a very happy moment and Hailey was taken off guard. Her face was in shock but you could tell they are both so in love."

Meanwhile, Ariana Grande - who recently announced her own shock engagement to comedian Pete Davidson - has defended Justin amid accusations that he's rushed into the decision.

After some fans claimed on Twitter that Scooter Braun - who manages both Ariana and Justin - had set up the engagements, the brunette beauty defended herself and the Canadian star as "human beings who love and have lives".

She wrote on the micro-blogging website: "You do realize we are human beings who love and have lives ...... right .... ? And that Scooter [Braun] is a wonderful human being too who cares first [and] foremost [about] our health and happiness? Love is lit. S**t happens. I hope to God it happens to you too. [You] deserve it. (sic)"