I don't see agree that you can compare a 60/17 sexual relationship with an incestual one.
Even if both involve consent, the key difference is that there is a body of medical evidence that shows that the risks of bearing a child with genetic defects would be greatly increased if a brother impregnated his sister.
As far as I'm concerned, the reason siblings can't marry is based on this medical evidence.
As for an older man with a younger woman, if he's virile and she's receptive, then go ahead, have a child.
What's the problem? Where's the harm? What's the risk?
I don't see agree that you can compare a 60/17 sexual relationship with an incestual one.
Even if both involve consent, the key difference is that there is a body of medical evidence that shows that the risks of bearing a child with genetic defects would be greatly increased if a brother impregnated his sister.
As far as I'm concerned, the reason siblings can't marry is based on this medical evidence.
As for an older man with a younger woman, if he's virile and she's receptive, then go ahead, have a child.
What's the problem? Where's the harm? What's the risk?