Do you remember when Britney Spears was a sweet 16 year old on the brink of super stardom? It’s hard to believe that over 10 years have passed since her first album debuted and we were introduced to the Spears clan. Not only did we discover the singer, but her manager mother, her dad, and her mini-me Jamie Lynn.

Jamie Lynn Spears was introduced to the world as Britney’s know-it-all little sister who was a spitting image of her sibling. She appeared in several films (Crossroads) and even had her own TV show called Zoe 101, before taking a break from the spotlight to raise her daughter. Today, we’ve realized that April 4 just past and it marked a very important day – Jamie Lynn turned 20 years old!

Spears made headlines back in 2008 when she announced that she was pregnant with her first child at the age of 17. It shook up her teen star image and definitely made us realize that our little Jamie wasn’t so little anymore. Fast forward three years later and she’s a happy mother who spends the majority of her time with her family, most notably her daughter Maddie.

Even though she’s just entering her 20s, Spears has felt like an adult for a while. She shed no tears over leaving her teenage years behind. Spears wrote on her Twitter page, “Goodbye teens.., Hello 20′s!!! Just got serenaded by Maddie’s preschool class – no present will top that!!!” It definitely seems like Spears’ attention is on more important things than aging.

Over the weekend Spears also tweeted a photo of her and her daughter hanging out together. It’s hard to believe that not only is Jamie Lynn an adult but she’s a mother. That wise-cracking kid we met a decade ago has ceased to exit. Happy Belated Birthday Jamie Lynn! Can you believe that Britney’s younger sister is already 20?