Some people have natural aptitude for art. This can be develped. Not only art, all have some latent talent that can be developed through training and practice. some times, a person with no initial aptitude may acquire talentin art.
I think when a child is born he or she has different ingredients of arts within them and if their arts are nurtured from an early age they could be one of the greatest in their field. Hence I feel artists are born and they are made into a complete one under the lap of mother nature...