People willingly choose who they associate with and they build their narrative to justify their choices. The people who choose to abandon their families (or a family member) often do so due to a conflict of interests. They willingly choose to break it off, blind themselves to the reality of the situation (which comes off as their side of the story) and refuse to make the effort to rebuild the relationship (due to their pride). At times, it can take a third party (like therapy) for the situation to work as one person can be saying one thing, and it has a completely different meaning to the other person (which is incredibly frustrating to deal with).

The same goes for any relationship. If a person is unwilling to sit down and make the conscious decision to make it work, the relationship will fall apart eventually when conflicts/misunderstandings arise, regardless if it is family, friends or a spouse. Think logically, not emotionally about what you have to do.