From an article in the MedicalXpress web site:
“Australian researchers from QIMR Berghofer Medical Research Institute have shown that 22 different genes help to determine how much sun exposure a person needs to receive before developing melanoma.
“For people at high genetic risk, sun exposure in childhood is a strong contributing factor while people at low genetic risk develop melanoma only after a lifetime of exposure to sunlight.
“The study results have been published today in the British Journal of Dermatology.”
In short, some people have a higher than average risk of developing Melanoma because of the DNA they inherited from their ancestors.