Hayden Panettiere & Milo Ventimiglia Split

02/17/2009 at 01:45 PM EST

Heroes stars Milo Ventimiglia and Hayden Panettiere have ended their relationship, PEOPLE has learned.

"They lead different lifestyles. He's 31, she's 19. She still has growing up to do and he's very low-key," a source close to the couple tells PEOPLE. "The relationship never seemed like it had legs."

The couple, who spent part of 2007 trying to hide their relationship, is still on amicable terms, another source says.

Reps for both actors would not comment.
– Monica Rizzo

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