Sofia Vergara is a happily engaged woman ... at least according to her 19-year-old son, Manolo Gonzalez.

The 40-year-old Modern Family actress is seen in this home video at her birthday bash in Riviera Maya, Mexico.

Gonzalez posted the fiesta on YouTube, as well as Sofia's proposal from boyfriend Nick Loeb.

In the video, Manolo says, "Once they were to the top of the pyramid, my mother's longtime boyfriend, Nick, proposed to her."

Crazy to think she has a son who's already 19! Lookin' good, mama.