Macaulay, best known as Kevin McAllister in the insanely popular 1990s 'Home Alone' movies, just announced the birth of his first child with his partner, actress Brenda Song.

Macaulay and Brenda welcomed their son, Dakota Song Culkin, into the world last Monday in Los Angeles. A rep for the couple says he was named after Culkin's sister who passed away in 2008.

The baby boy is healthy after weighing in at 6 pounds, 14 ounces.

It's pretty jarring to think of Macaulay as a father and not as little Kevin ... entire generations have grown up knowing MC only from his classic Christmas movies, and the Google holiday ads reprising his iconic role.

In fact, filming wrapped on the OG 'Home Alone' a few months before Macaulay's 10th birthday, and he was 11 years old when he played Kevin in the 1992 sequel.

Now, he's a first-time father at 40 ... and with baby Dakota joining the fold, Macaulay and Brenda will no longer be home alone. Also, their sleep will most likely suffer.