Well -- yes and no.
Yes, because the Elite Royal Guards were "GeNode" Clones, meaning that they were all identical clones of each other, but not of Jango Fett at all, and they had implanted memories and identities so they didn't know they were clones.
No, because a) stormtroopers after a certain date weren't clones any more, as Jango's genetic material was basically degraded and you couldn't copy any more from that source and b) the Royal Guards existed before the Clone Wars (since they're in Episode II).
So I guess it's the same answer as when people ask if the stormtroopers were clones:
Depends on which Royal Guard you're talking to - maybe, maybe not.