What is is 1999 a millennial?

No, someone born in 1999 is generally not considered a Millennial.

The Millennial generation is typically defined as those born between the early 1980s and the mid-to-late 1990s. While there isn't a universally agreed-upon cut-off year, 1996 is often used as the last year of birth for Millennials. Therefore, someone born in 1999 would more commonly be considered part of Generation%20Z (also known as Zoomers).