Well, Sarek is set in 2293, about 26 years after "Operation: Annihilate," so Peter would've been around 38 or so at the time. According to Wikipedia, Liam Hemsworth is only 23.
Christopher, he's Chris Hemworth's brother. That was why it came to mind.
I know Peter's age was explicitly mentioned in Sarek
, but it's been too long since I read it and I don't have access to my collection at the moment. I could've sworn the book said he was 28 either at the time or when he joined the Academy, but that would've only made him about 2 in "Operation: Annihilate!" so that doesn't make any sense...