Certainly...
A system is the family group:H/W and childen.In most of the cases on this board,I would venture to say there has been some degree of dysfunction which is acted out in various family members.

By shakey...I mean that there is "dischord" with the family unit,perhaps more intolerable to some than to others.Example...difficulties with children and childraising issues,career difficulties,role changes etc.,lack of attention to spouses,etc.
It may be overwhelming and difficult to pinpoint what the real problem is,but some sort of CHANGE is desired...here comes the quest for a divorce..to get away.
When one person is the system "gets well" or changes in a positive way it causes others in the family to change,too.(DBing philsophy)

I believe that often the person that appears to be the "sickest"(MLC or whatever)is a symptom of other problems in family or relationship.Some of us our stronger and more persistent in holding thing things together during uncomfortable periods,while others have a lower threshold for discomfort.
Just a few thoughts...