Quote Originally Posted by Inverarity
Why? There are lots of entertainer families with children who are quite a few years apart. As for Merton being younger than Hermione -- remember that not all wizarding children go to Hogwarts. Maybe she's privately tutored, as many child stars are.
The problem I see with that is that they are supposed to be some super cool rock band (I always imagined them to look like wizarding Kiss) and that they (if I'm not mistaken) played at the Yule Ball so one of them would have been 13 or 14 then. Yeah I bet all the 17 year old girls were lying at his feet!

But apart from that it's a good explanation. Sort of Jackson- or Kelly-family-like. Maybe even a casted band... Look at all the teen pop stars nowadays. But still, they aren't a rock band that everyone in the (wizarding) world listens to!