While in the US it's one here and one there, in Italy/Sicily it's common. Behind every top mafia man is his woman. They hold onto grudges longer and make sure their husbands/sons/brothers never forget. They groom their sons to take over for their husbands. They don't go on tv and talk about it, they don't talk about it between girlfriends, but it's known.
They will never be made though. In Italy, a woman married to a mafioso is not considered an accomplice and can never be forced to testify. If she would be a made woman and formally inducted into the mafia, the rules change. And when their men go away, it's their women who they rely on to keep the lines of communication open and carry on what's needed. They're more ruthless than the men, believe it.