If I was born in 2000, would I be born in the same decade as someone born in 1999 or 2001?

You were born in a new decade

So 2001

2000-2010 would be your first decade. if you were born in 2000 you'd be nineteen and just developing sexually as a female. If you were male you'd develop earlier since men hit puberty earlier than females.

So while your born decade is the first decade and men will identify it that way for yourself most females identify with the second decade because it's usually later on in it or the third decade they usually find a husband get married and have sex.

Same decade as 1999.

I would assume 2001

I'd answer you, but you'll just keep asking the same dumb question over and over again. Go seek a life.

Sure. If you weren't then use your imagination, know a days you can 'identify' as being born in the same decade as someone born in those years you mentioned and YOU MUST BE BELIEVED AARRRRGGGHH!