Nope, don't feel any pity for him. If there weren't any mitigating circumstances that affected the sentence, then there's no reason to feel bad for him. Maybe he should have been given possibility for parole after 30 years or so, but of course, I'm not the lawyers or the judge or the jury involved in the case.
And I'm not sure what you're getting at. He'll serve more time because he's younger? Well duh. But that's because he committed the crime when he was 13. If we would have been 80 when he committed first degree murder, the sentence would have been less. Take that issue up with God.