Justin Bieber & Selena Gomez Rekindle Romance: Kourtney Kardashian & Hailey Baldwin React On Instagram

Selena Gomez and Justin Bieber are using Instagram for some flirty fun, and fans of Jelena are loving it. It all began when the 22-year-old pop idol posted a throwback photo showing him exchanging a seductive kiss with Selena, reported the Daily Mail.

"Perfect," posted Gomez.

The Instagram photo that Selena liked so much bore only the caption "Feels," but the feelings apparently overwhelmed Jelena lovers by garnering millions of likes (in addition to Gomez).

Now, following the excitement over that Instagram picture that served a way for Selena to show she hasn't ended her affection for her off-again-on-again boyfriend, Gomez has come up with her own throwback picture, noted Us Weekly.

Selena has shared her own throwback photo showing herself seated at a piano bench sporting a very becoming bikini.

"tb to a sweet, small house in TX," wrote Gomez for the caption.

When Jelena fans saw the picture, suspense reigned as to whether the Biebs would respond. And the answer is "yes," as the 22-year-old "Sorry" singer indicated he "liked" her post just as she had "liked" his lip-lock pic.

And it didn't end there. In addition, Selena was seen at her ex-boyfriend's concert, held at the Staples Center in Los Angeles. Fans noticed Gomez relaxing in the sound-mixing area during Bieber's Purpose World Tour and spread the word of their apparent reunion.

Are Selena Gomez and Justin Bieber back together?
Are Selena Gomez and Justin Bieber back together? [Photo by Pascal Le Segretain/Getty Images]How is all this affecting the Bieb's off-again-on-again hookups Kourtney Kardashian and Hailey Baldwin? Sources say that Hailey is having a hard time accepting her former boyfriend's renewed romance with Selena, according to IBT.

After learning that Gomez had been seen at the concert, Baldwin is "agonizing" and seeking for acceptance. Hailey even followed the lead of Jelena by turning to social media herself to show how she feels.

But Baldwin went one step further by emphasizing her goal of staying grateful.

"no matter the circumstance," added Hailey in her caption.

Although Baldwin wishes she could be Justin's only girlfriend, she's determined to look at the positive elements in her life, revealed an insider to Hollywood Life.

"When he goes hot and cold on her like this it hurts her a lot more than she lets on. This whole thing with Selena is agonizing for her," said the insider.

Justin Bieber hurt Hailey Baldwin?
Justin Bieber hurt Hailey Baldwin? [Photo by Kevin Winter/Getty Images]However, Hailey is aware that she has a successful career as well as potential boyfriends in her favor.

"Hailey isn't going to sit around crying, she has a career that's on fire and so many guys after her so she's doing her best to focus on all the positive things in her life and accept the way things are," added the source.

As for Kourtney Kardashian, the Keeping Up With The Kardashians star is determined to keep her public face positive with some help from her family and friends. First, Kourtney went to his concert with friends Malika and Khadijah Haqq, plus rapper Big Sean, noted the Daily Mail.

And following the same instinct that caused Selena, Hailey, and the Biebs to show their feelings on social media, Kardashian revealed that she's on Team Belieber with her own Instagram photo.

And apparently, Kardashian had so much fun that she decided to show her carefree attitude about her boy toy by partying with the Biebs, Kanye West, and Kim Kardashian, according to People, which reports that multiple sources confirmed Kourtney and Justin had hooked up last year.

But at the party, Kardashian and the Biebs kept cool about each other.

"Justin and Kourtney were social, but you could tell they kept to themselves on purpose. There was no coziness," revealed a source to People.

[Photo by Dimitrios Kambouris/Getty Images]