I have never heard of a hidden gene lesser. There is however a mystery surrounding the original Platinum that lessers originated from. it seems that the only way to reproduce a platinum is with a lesser and a lesser sibling that looks normal. That would be the hidden gene.
The soul sucker is no mystery. Kevin has made it well known the HG Woma is actually a different mutation from the regular woma. It just looks like a regular woma. The soul sucker is a HG womaxlesser...