The duo, who earlier dated in 2016, had fuelled speculations of reunion among fans in recent weeks by appearing together.
Bieber's father, Jeremy Bieber, also teased the fans with a cryptic social media post.
"@justinbieber Proud is an understatement! Excited for the next chapter!" he captioned a photo with the younger Bieber at the beach on his Instagram.
The "One Time" hitmaker's mother, Pattie Mallette, tweeted "Love Love Love Love Love Love Love", offering no further explanation.
"He is moving in the hearts of JB & HB. Let's all pray for His will to be done. Love you 2 so much!!! #Godstiming #bestisyettocome," the elder Baldwin said in the tweet, which also tagged Bieber's parents to congratulate them.
The initials 'JB' and 'HB' may allude to the engaged couple's names.
This tweet, however, was quickly deleted.
While Bieber, 24, last dated his on-again, off-again girlfriend singer-actor Selena Gomez, Baldwin, 21, was recently linked with singer Shawn Mendes after the pair attended the Met Gala in New York together in May.
The couple is yet to directly comment on their relationship.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)