Is This Normal?

Is it normal that I'm only attracted to women who have sons?
She can have other kids but there must be at least one son for me to be attracted to her. I feel absolutely no attraction to women who have only daughters or even no kids. As soon as I hear that a woman has a son, I instantly become attracted to her. It doesn't matter if she's married or not, as long as she has a son, I'm attracted but I know the limits when it comes to married women.
Is this normal and do other people experience this aswell?
Also, is there some underlying issue that's causing this?
Please help. It's actually affecting my life at this point.