Natalie Portman began her acting career in the short film Developing. She was just 13 when that short film was released. She filmed many movies before becoming an adult. Her busy acting career and Harvard education certainly would have impacted the time she had for dating.
The pair are rumored to have dated during Star Wars. When Star Wars: Episode 1 - The Phantom Menace started filming in 1997, Portman was only 16. She was 19 when the second movie was filmed, and she was allegedly dating Christensen when the first movie was released. At that point, she was also enrolled in college and working towards her degree in psychology from Harvard. Hayden Christensen is not the only actor she's rumored to have dated before her later marriage. MTV also says she dated Jude Law and Sean Penn.
In 2010, Portman became engaged to Benjamin Millepied, her choregrapher in Black Swan. She gave birth to their son, Aleph, in 2011, and the couple married in 2012.