If you are asking "Who are the Mansons?":
I have never seen the show but they are probably referring to the Manson Family, a community lead by the murderer Charles Manson who were thought to be crazy due to the fact that they believed in what Manson told them.
If you are asking "Why do the Mansons need some time apart?":
To quote the Wikipedia article linked above,
They [the Family] roamed as far north as Washington state, then southward through Los Angeles, Mexico, and the southwest. Returning to the Los Angeles area, they lived in Topanga Canyon, Malibu, and Venice—western parts of the city and county.
implying that they were very close, having lived in a van together for months.
I hope that answers your question.