re: Most men can resist the temptation to make a pass at their wife's sister.
That's rather funny.
I've been reading a lot of history about this area, the founding fathers and all. And quite a few brothers and cousins stepped in to marry the widows when their husbands died.
But that was because they were bound in small settlements with lots of property and it was easier to keep it in the family.
No real transportation or all the accrutements that a current suitor would have to get out and really SEE what else was out there.
PS
If your wife's sister really did come on to you, would you tell your wife?
Some women just like to tease and stir up trouble, especially if there was some jealous competitiveness going on between them.