Scared to have baby with boyfriend

This is for future reference because I am not pregnant right this second and I don’t plan to be for a while but I am freaking out and just need a answer to this horrible question. So my boyfriend who I am 99% sure I am going to marry has a sister who has a skin condition. His sister let’s call her A well A had a baby and her baby has a rare skin condition called epidermolysis bullosa. I have done much research and have seen that it is contracted through the genes and that most child with EB do not live a very happy long life. My question is since A has a skin condition does that mean my boyfriend could have the gene for a skin condition as well ? They both have the same mother and father but he shows no symptoms of the skin condition she has . I don’t want to live my life in fear of what could happen but I have to know before I ever even think of having children. It’s bugging my mind and eating me up inside so someone just answer my question of if one sibling has a skin condition does the other sibling have the gene for it as well ?