Mine usually are as well, though I have been making some attempts to ensure that's the case. I haven't quite been trusting enough to allow the sexes to mix unsupervised, and I've been lucky so far.

[...so far.]

...though, when they go at it, they really do go at it... well, anyway. Emploeon's one I've been interested in obtaining for a while, but I've never quite had the opportunity to pick up a Piplup and I haven't the faintest idea why...