No women are inducted into the Mafia. Women are of no consequence in the Mob. Wives of made men aren't even acknowledged. A made man is expected to "keep his family in line," meaning that he's responsible for making sure his wife doesn't rat him or any other Mob guys out. Presumably he could be ordered to whack her if she "stepped out of line." The only "rules" that apply to wives are that a made guy cannot fool around with another made guy's wife; and that a made man is supposed to be "loyal" to his wife--which means that he can have girlfriends and mistresses galore, as long as he doesn't divorce his wife or "disrespect" her by cavorting "openly" with a mistress or girlfriend. "Openly" is open to interpretation (usually in favor of the man).
Very few Mob bosses have trained their sons to take over, mostly because they'd prefer their children to be successful in the legit world (or as close to legit as they can get). And in those few cases where Mob bosses have expected their sons to take over, they've caused heaps of trouble with others in the family who had their own expectations--attest Alphonse (Allie Boy) Persico, Salvatore (Bill) Bonanno and John (Junior) Gotti. An out-and-out war is the likely outcome, so the Don tends to keep his intentions quiet. You must be thinking of Charlie Chan designated a pecking order for his boys: "Number One Son, Number Two Son," etc.