When Britney wed backup dancer Kevin Federline in a surprise ceremony Sept. 18, she also became a stepmom to his daughter Kori, 2, and son Kaleb, born in July (not pictured), both by his ex-girlfriend, former Moesha actress Shar Jackson. As for Britney, "I want to be a young mom," she told PEOPLE after marrying Federline. "Next year at 23, I am so there."