<<snipped>> I'm afraid it is one of those areas where logic seems to have played very little part in formulating the laws. There is no blood relationship between a man and his dead wife's sister, so it is difficult to understand why such marriages were void anyway. <<snipped>> If I recall correctly, the "logic" behind this was that a man and his wife became "one person". Therefore the wife's sister became the husband's sister and the husband could clearly not marry his own "sister". Adrian B