A genetic predisposition does not necessarily involve a single gene, it may involve a combination of genes. If one looks back over generations and sees a pattern, then a genetic factor is a possible explanation.

It seems in the case of Barbara's son, such an explanation should not be ruled out. Otherwise, on the whole, I agree with you, Jim.

I'm one of those who kept being told be couldn't sing till I found out otherwise. My regret was I believed them, in spite of evidence to the contrary, having sung when I was younger.