The bio sections on this site are worth a read, in particular the McVie info as John gave Lis (former site owner) edits, IIRC.
http://www.fleetwoodmac.net/fwm/inde...d=73&Itemid=89
Here's an excerpt CM quote
I daresay, if I hadn't joined the band, we might still be together. I just think it's impossible to work in the band with your spouse. Imagine the tension of living with someone 24 hours a day, on the road, in an already stressful situation, with the added negativity of too much alcohol. It just blew apart." Anyone who has taken a holiday with someone knows how after about a week in close quarters, tempers start to wear thin, and little irritations start to grow into major blow-ups. I can’t fathom the strain of doing this for years instead of days or weeks, and dealing not only with your spouse, but also with the little idiosyncrasies of other individual band members. Add to that a poor diet, cramped travel cars, a nightmarish laundry situation, dirty hotel rooms, and lack of privacy--Mick has said that at times they had to sleep three or four to a room-- not exactly a recipe for marital bliss. But the root of the problems really seemed to lie in the fact that they were just together too much: “John and I spent too much time in each other’s pockets. It’s pressure, being in the public eye. When people get married they can live in a house with more than one room. But on tour you’re in a hotel room together, you leave the hotel together, you drive together, eat together, sit on the plane next to each other—you’re like Siamese twins.”