This also raises the consideration of what might have been said about each others families while they grew up.

For instance: I know of a boy, who I will call "Kirk" who has 3 half siblings but only 2 of them are related to each other. He is the result of his parents first marriage. He has a 1/2 brother from his dad's 2nd marriage. Let's call that brother "Jacob". Kirk has a 1/2 sister and another 1/2 brother from his mother's 2nd marriage, "Victor" and "Mary". While growing up, the ex's had many verbal telephone confrontations, and even took each other to court over custody of Kirk. Because they lived 1000 miles away, the 1/2 brother Jacob never met either of the other 1/2 siblings, and vice versa. The one thing the 1/2 siblings did share, was contempt for their parents ex spouse. This being the case, if Mary grew up and met Jacob and started dating him, she would never think he might be related to her family, because they lived 1,000 miles away. Once she found out, however, she should not continue to date him. This is because both families probably have bad blood between them somewhere along the line, and loyalties are very difficult for adults to have when they formed loyalties to their families as children. Those are the strongest ties, family bonds learned as children. It would break those family ties to bond any further with such a person.

So, my answer is NO, I would not date my sister's brother!