While walking the gold carpet at this year's Emmys, the Mission: Impossible - Fallout star told reporters that they had already tied the knot; "They went off and got married, and I don't know what the deal is!"
However, Alec won't be talking to Justin about any advice he may want to share - as he wants to leave that up to Hailey's dad Stephen.
The US model, 21, and Canadian singer, 24, were spotted at the marriage bureau at a courthouse in New York City last Thursday, prompting the model to deny wedding rumours. Bieber was born and raised in Ontario, Canada but has lived in the United States since he was 13 when he moved with his family to Atlanta.
Alex Baldwin just revealed in an interview that Justin Bieber & his niece Hailey Baldwin are indeed married! "But marriage is two people making a vow before God and the people they love", added a religious source, confirming to PEOPLE that they were legally married at the courthouse but are planning to have a religious ceremony and celebration with family and friends soon. She later deleted the tweet.
The "legal insider" claims that Bieber and Baldwin do not have a prenup.
The couple had dated in 2016 but broke up.
Seeming to forget they were out in the open, Justin caressed her face as the pair enjoyed a very steamy kiss. She wrote: "I understand where the speculation is coming from, but I'm not married yet!". And my wife and I had four kids in four-and-a-half years.
However, Hailey's uncle, actor Alec Baldwin, has seemingly ignored their denials, and confirmed that the pair have been married for almost a week.
Hailey Baldwin was equally as enthused in her post about Bieber. "I don't know what the deal is".