Re: Why????
grabs his devil horns and red cape Time to play devil's advocate.
Children are a product of their upbringing and the manners in which they grow up. Though brothers and sisters are similar in many ways, they are individuals. But their upbringing is the same. The same moral values and the same standards in life. That means they have similar views on what they want out of life and expect similar things from their spouses.
These issues could be very core reasons to trivial stuff. But once there is a bad or a failed marriage, it comes down to what people want out of life. Those could be issues the sisters have.
Basically if one girl is a *****. Probability is pretty high her sister is as well.