It because they think no one is good enough for their loved one ... no one is better than another and its all about maturity soon if she really loves her brother she will cut it out and grow up or the other way around its not about sex its about piece of mind
Often a wife will feel that she is not as much a family member as her husband's own mother, father, and siblings. This also affects husbands in their relations with the wife's family (his in-laws). It is not unusual to find conflicts between sisters-in-law: the sister has normally known her brother for all of one of their lives, while the wife is the newcomer who nonetheless is now the man's primary partner in life. More than a little jealousy can exist both ways. Parents of married couples are likewise liable to criticize the spouse rather than their own child (although exceptions do exist).
People can be jealous for many reasons, most of them personal and many irrational. It is not possible to say why in general one group is jealous of another.
Hera
CeLsIuS hAd No BrOtHeRs oR SiStErS ... So He OfTeN FeLt LoNeLy...:( :(
sisters often miss brothers while brothers hardly miss sisters because nomatter what the brother does the sister never holds a grudge nomatter how much she wants to while the brothers normally hold a grudge.
If he does hold jealousy for his brothers, it would be because they are often more revered than he. But, he does not hate them.
His grandmother had often told him of the hardships herself and her brothers and sisters faced as children.
In some cultures, some jealousy of the husband's family members may be that they are feeling like they have to compete with then or are feeling judged by them. In other cultures jealousy of this sort is not common.
She was a very jealous and vengeful goddess so she didn't take it very well. She often tried to prevent the births of Zeus's lovers' children or, if this failed, she would put obstacles in their paths.
Because we often see her jealous when Zeus is off with another women
They're not ditching you. They're in love. They're not being selfish. How'd it feel for the boyfriend if she ditched him for you? They've got less time on their hands.
Hera is the Goddess of marriage so she would be jealous of her husband Zeus's affairs.
Hera was the Greek goddess of women and marriage. She was the wife and one of three sisters of Zeus, the "king" of the gods and thus was the queen. She was a jealous and vengeful goddess, often against Zeus's lovers and their offspring. Her main symbol was the peacock.
A jealous significant is person that is jealous of his/her significant other. For example, a divorced man's new girlfriend may be jealous of the divorced man's former wife because he still thinks of her, or talks about her often.