"my elder sister"
Actually, in my experience, おれ is very frequently used by males in informal speech, much more so than ぼく.
I think おれ carries more gravitas, and roughness in the form of male dominance, so older men will use it exclusively, even in some formal situations, while young boys tend to use it when they want to sound tough and cool.
ぼく on the other hand, is masculine, but in the boyish sense. I, a 26 year old male, use it exclusively and my partner, a native Japanese speaker, tells me she thinks it's childishly cute that I don't use おれ.