The stealth birth was announced by the Star Wars actor's daughters Clara, Esther and Jamyan McGregor, who shared photos of the baby boy they report is named Laurie.
"Welcome to the world little brother," Clara, 25, wrote with a photo of her holding her newborn sibling. "Congratulations to my Dad & Mary — this is the greatest gift."
Esther also shared a shot, writing, "Met my little brother looking like a pirate. I recommend! Welcome to the family little Laurie," who shares a name with a famous character in Louisa May Alcott's Little Women.
Jamyan, 20, also shared a picture of "our little man," noting Laurie "came into the world on June 26."
McGregor, 50, and Winstead, 36, did not publicly announce the pregnancy — nor have they announced the birth of their child.
Baby Laurie is McGregor's first son. He also shares daughter Anouk, 10, with ex-wife Eve Mavrakis.
McGregor and Winstead met making Season 3 of TV's Fargo in 2017 — and their romance blew up the internet. After they were spotted kissing, it was revealed that their respective marriages had come to an end. At the time, he had been married to production designer Mavrakis for 22 years while she and Riley Stearns had split after seven years of marriage.
While it was initially a bumpy blending, they seem to be a happier family now.
The pandemic has allowed some celebrities to keep pregnancies low-key, also including Emmy Rossum, Mindy Kaling, Troian Bellisario and Jessica Biel. However, McGregor and Winstead have been pretty secretive, so they probably would have kept it quiet, pandemic or not.
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