Interesting read here about melanoma.
http://www.nhs.uk/Conditions/Malignant-melanoma/Pages/Causes.aspx
In my opinion (I'm not a medic) reduced sunbathing and non-use of sunbeds would have reduced risk, but other factors are also involved.
In April 2013 I was diagnosed with a malignant melanoma (stage 1a?) on the left leg about 6" above my ankle which was removed and I had a skin graft.
I have never used a sunbed and rarely sunbathed without a highish factor suncream/lotion. However, I do have fair skin, blue eyes, fair hair and am getting older (65+) which puts me in a higher risk category.
Apart from removal I then subsequently had a sentinel lymph node biopsy to confirm an all clear status. I still go for 6 monthly checkups and was told I can expect to do so for at least 5 yrs.
Has your nephew got a result on the biopsy yet?