The Peacock's Pearl

I was hanging out with Elizabeth when I saw the boy again. Not just a boy, but that boy, the one you sort-of
notice, but only to think, hey, wasn't he here yesterday?
He glided by Elizabeth's hedge on his bike once too often, giving that sliding sideways glance he hoped (I
expect) looked casual, disinterested and, oh, there's that chick again, hanging out with her big sister...or is it her auntie? Too old to be a friend.
Elizabeth is my great-great-great-great-great granny, for your information, Bike Boy, I thought-spoke
to him on the fourth bypass of the week.
He toed his pedal down and skimmed away before getting into some serious calf-work as he headed up the hill towards Caroline Court.

Who is Bike Boy and why is he interested in Cat and Elizabeth? Is he just an ordinary boy, or can he be out for Restitution and Revenge (and not necessarily in that order)?

Cat Mahal has an ordinary life in the suburbs.
She is also an ethical witch.