>>57806902
1. It could be like Butterfree and Venonat and many other designs with very similar traits; they share the same creator but are otherwise unrelated.
2. They were one of the first Gen3 designs to be finalized, to the point that they could appear in the Gen2 anime- much like how Togepi was introduced during Gen1. Maybe they considered making them related, until they decided that Misty having a baby Legendary was too much.