I am wondering - why is it that an ex-husband is called so, and the same does not apply to an ex-sister, or an ex-son?
In life, there are times when people move on beyond the blood relations that they have, and become strangers to their brothers and sisters, and sometimes to even their parents. People often times don't talk to their parents anymore, or don't meet their brother for years, or disinherit their son for some misdemeanor, and so on.
Blood will be blood, people say, but I haven't found it to be so. People can and do drift apart, sometimes they push people violently away from them, despite being bound by bonds of blood. I know of so many like that.
Just like marriages and loves, people do move beyond the ties of blood, and become ex'es, Why are they not called "ex" too?