Hard to say about the 1st case, could be a mutual

dependent situation.

For the 2nd case, clearly a good, effective parent-child communication have been missing since the childhood(?). Pushing alone doesn't directly cause the cut off in relationship with the parents. 

If the parents and child have a good communication and connection all along, the child normally would not stay away for long. Most would maitain a normal relationships with parents after late 20's.