Looks like the age difference between “Heroes” stars Hayden Panettiere, 19, and Milo Ventimiglia, 31, has finally caught up with them and they decided to split.

The two actors, who have been in a relationship for over a year, are being very mature about their breakup and remain on friendly terms, probably to avoid awkward moments between them while they continue working together on NBC’s superhero series “Heroes.”

“It was a lifestyle conflict,” a source close to the couple told Usmagazine.com, adding that the split happened within the last week. While Hayden is “young and wants to go out in the Hollywood scene,” Milo would rather focus on his work and his production company “Divide Pictures.”
 
“They were in very different places,” the source said.

The actress was reportedly seen kissing Jessie McCartney earlier this month.

“She still has growing up to do and he's very low-key,” another source told People magazine. “The relationship never seemed like it had legs.”

Rumors that Hayden and Milo were dating began in September, 2007, with the couple finally going public with their relationship in January, 2008. Dubbed by tabloids and celebrity gossip blogs “Halo,” the pair was subject to much media scrutiny because of the 12-year age gap.

During their relationship, there has been a consistent rumor that Milo wanted to marry Hayden, (they have been dating for over a year, that’s practically a lifetime in Hollywood) but that she wasn’t ready for such a commitment.

In the past, Milo dated “Gilmore Girls” co-star Alexis Bledel, then left the show and they broke up at the same time, after 3 years of dating.