I was hoping the oldest would be a boy because just like us humans the Roo boys mature so much slower I feel
That does not match my experience.
I have seen that males are typically trying to mate quite a bit before their sisters start laying eggs. I've also seen threads where other people have issues with that, a male trying to mate with his same-age sisters or flockmates, who are smaller than him and not yet ready. Full mature size might take longer for the males (I'm not entirely sure), but sexual maturity seems to hit most of the males earlier than most of the females.