Alongside a picture of her newborn daughter Lucia, Baldwin wrote on Instagram Stories: “I know… I know, sleuths….my skin is darker and my kids’ is lighter.
“Yes, they are mine.
“Trying to keep up with all these ideas…I have to say: you have quite a bit of time on your hands.”
The couple are also parents to sons Romeo, Leonardo, and Rafael, as well as daughter Carmen.
In 2019, the couple suffered a miscarriage four months into the pregnancy. They had already lost another child earlier that year.
Alec is also father to daughter Ireland with ex-wife Kim Basinger.
Hilaria Baldwin dismisses parenthood claims about her daughter