I spent a couple hours yesterday around noon bicycling around town. When I was done my arms were hot and I could see a clear difference in skin colour between the part that my bike jersey covered and my exposed arms. I had forgotten to put on sunscreen because it was a bit overcast when I started out.
Last night I ordered UV sleeves and coated my face and arms with a liberal amount of sunscreen for todays trip ride. Once the sleeves arrive I'll be able to wear those with all my short sleeved jerseys.
I have no knowledge of family medical history so for me I'm just going to stay safe, cover up as much as I can and wear a lot of sunscreen.