Hollywood actors Hayden Panettiere and Milo Ventimiglia have ended their yearlong relationship, a source close to the "Heroes" co-stars told Us Weekly.

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"It was a lifestyle conflict," the insider said, noting the breakup happened within the last week. "They were in very different places. ... They are still on friendly terms. There are no hard feelings."

The source said the couple's 12-year age gap played a role in the split.

"(Panettiere) is young. She likes to go out in the Hollywood scene and that's not his style," the insider said of the 19-year-old actress and her 31-year-old former beau.