Among the thousands of responses, some of Baldwin's former classmates claimed the yoga instructor grew up in the US and went by the name Hilary, not Hilaria.
"I went to high school with her. Genuinely lovely person, I recall, but fully a white girl from Cambridge," wrote one user.
"I went to high school with her. She was perfectly nice and serious about ballroom dancing. Her name was indeed Hilary Hayward-Thomas and she did not have her current accent," shared another.
Many posts on Twitter have also expressed confusion, intrigue and anger over the star's changing identity.
"Hilaria Baldwin aka Hilary Thomas is the weirdest story I've heard this year. Faking a whole persona and accent this whole time? Her parents are white and from Boston. There's no way she was born in Spain since her mom (sic) was in med school in Boston in 1984 (graduated in 1986)," wrote one user.
"Remember when Hilaria Baldwin (nee Hilary Hayward-Thomas) was like "how you say in English, uh, 'cucumber'"?" shared US-based writer Sophie Ross.
"I'll give Hilaria Baldwin this – when she commits to a con, she COMMITS. She even gave her children Spanish names. Hilaria from Majorca is really Hilary from Boston. You can't make this sh*t up. What's the Hispanic version of blackface?"
Their confusion is warranted. Previously it's been reported the mum-of-five and wife of Alec Baldwin grew up in Mallorca, Spain and can be heard speaking with a Spanish accent in several media interviews.
Baldwin herself also claimed on the #mumtruths podcast that she moved to the US when she was 19 to go to New York University.
"My family lives in Spain, they live in Mallorca," she confirmed to the hosts.
Her talent agency bio with the Creative Artists Agency also confirms that Baldwin was "born in Mallorca, Spain and raised in Boston, Massachusetts".
Clarifying the confusion in her Instagram video, however, Baldwin has now confirmed she was born in Boston, Massachusetts and not Mallorca, Spain.
"I was born in Boston and grew up spending time with my family between Massachusetts and Spain. My parents and sibling live in Spain and I chose to live here, in the USA," she wrote in the caption. "We celebrate both cultures in our home – Alec and I are raising our children bilingual, just as I was raised."
She also admitted that being bilingual, her accent does fluctuate.
"I am that person who if I have been speaking a lot of Spanish then I tend to mix them and if I've been speaking a lot of English then I mix up my Spanish," she said. "It's one of those things that I've always been a bit insecure about. When I get nervous or upset then I tend to mix the two.
"It's not something I'm playing at ... I want that to be very, very clear."
Finally, when it came to her name, Baldwin said that while she used the name Hilary in high school, she's known to her family as Hilaria. She later "consolidated" her name as Hilaria as it was administratively easier.
"One of the things I love about what my parents called me, it means happy in both languages, we can all be really clear that it's the same name, it's just a few letters different, we shouldn't be so upset about it," she said.
Earlier this week, Baldwin also received criticism over a "post bath" Instagram photo in which she can be seen holding her 3-month-old son in her underwear.
Comedian Amy Schumer re-posted the image in a now-deleted Instagram post, with a tongue-in-cheek caption which read: "Gene [Schumer's baby boy] and I wanted to wish everyone a happy holiday season. Enjoy it with whatever family members are talking to you this year."
Expressing confusion over the post, Baldwin said Schumer's post resulted in many comments which body-shamed her post-birth figure.
"Love a good joke – don't think this should have been such a big deal," she said on an Instagram video shared on December 23. "My only concern with it is that it started to spiral out of control ... where we're getting into a place of body shaming.
"The problem is sometimes we put down people's shapes ... If you're doing body inclusivity then that means body inclusivity for all."
Baldwin later followed it up with her own joke.
"Looking forward to much positivity in 2021 – like Alec carrying our next child ... thank you @amyschumer for being a part of our pregnancy announcement and convincing me that after five children, I've done enough," she wrote, sharing a photoshopped image of Schumer and herself and Alec.
