sorry, thinking about this, the term geno-photodermatoses probablyt direactly means, genetic, dermatitis caused by sunlight. So a very general term. Back to the drawing board.
You say this is in your mums family, just her sisters? Is this in any cousins etc on either grandparents side? If it is not, i would wonder if the inheritance is recessive, meaning you would need two copies of a faulty gene, one from mum, one from dad to be affected. That being the case, for you to have inherited and displayed symptoms your dad would have to have the faulty gene too, and if you only inherited one copy then you might be a carrier but again, your childrens partner would also have to be a carrier, if that makes any sense. If this is a dominant condition (meaning only one faulty gene copy required to display symptoms) you wont be a carrier. Of course there is a 50 50 chance of inheriting the faulty gene so it might not continue in your bloodline. Does that make any sense? This is total guess work based on what you have told me about your family. Has it only affected the women in your family?