Common for many who suffer from Vulgaris to have carriers in both sides of the family. Let us assume one parent has symptom and the other does not, but extended family of second parent shows symptoms. Some of the children of these two people may have mild symptoms and some may have severe symptoms. If those with mild symptoms have spouses whose families have no symptoms, their children may show no symptoms at all.
If you have severe Vulgaris, which is rare, you may have bad scaling that could lead to prickly itch. I do not know if your severity would or would not increase the chance of you passing the condition on to your offsprings.
Seems to me all you could do is find a spouse who shows no symptoms to maximize your chance of having children with no ich. Easier for you to do this in a large and cosmopolitan city rather than a small town or village where ich may be more prevalent.