Ewwww... You do know that Reever is ten years older than Lenalee, right? Allen may look young, but he's really only about ten months younger than Lenalee (or possibly two years if Hoshino did screw up the ages/times worse than I suspected - but even then, that's not a big age gap. He's closest in age to Lenalee than anyone else). Anyway, fifteen isn't really that young. We're talking about a shounen series, not a who-should-legally-sleep-with-who (with the age of consent thing, in which case Allen, Lenalee AND Road should all not be here).