I'm on the paleo diet and am the main cook, but my wife isn't on it, and isn't the least bit interested. And she has a completely non-Paleo diet if there ever was one. She eats lots of processed carbs (Eggos for breakfast, bread or pasta with lunch and dinner, 2 scoops of sugar in her coffee, a coke or two a day, etc). She eats a LOT of vegetables, greens with almost every meal, and could happily live on starch and vegetables with the occasional meat or fat.
She is perfectly healthy and happy, fit and slightly underweight (5'8" 120#), the same weight she was in college (after 2 kids), Yoga instructor, good muscle tone, rarely gets sick, etc. She is a complete anathema to the Paleo diet. If I ate this diet, I would suffer greatly, but there is no question that it works for her.
For dinners we do a Jack Sprat kind of thing, usually cook a trinity of meat, starch and veg, I will have maybe 2 portions of meat and 1 of veg, she'll have <= 1/2 portion of meat, 2x portion of starch and veg, and the kids eat some mix of these.
I feel very strongly that the Paleo diet is best for me. However it is plainly obvious that her diet is good for her. This is a constant topic of conversation in our household, since we eat totally different diets. We also talk about it with friends and family.
We also require totally different kinds of exercise, I need intense cardio (i.e. running, biking, competitive sports), she needs calmer stuff like walking, yoga, meditation. You could say that I'm the hunter and she's the gatherer.
I do have a Paleo-friendly explanation for this though. The Paleo theory says that humans have only be agrarian for ~10,000 years. Well it stands to reason that some humans on the earth have been agrarian for longer than others, and after 350-400 generations have evolved to be ok with this kind of diet. One interesting factoid that we discovered was that she has an extra loop of small intestines compared to the average person, something that some other people in her family also have. An evolutionary adaptation perhaps?
We have two kids, and one of them is like each of us. My son (age 8) eats a very varied diet including meat, fat, organ meets, raw fish, pretty much anything I put in front of him. My daughter (age 6) is more like my wife and it is very hard to get her to eat anything but starches and fruit, though once a week or so she pigs out on some kind of meat or fat. Both kids just had their checkups and are perfectly healthy and near the center of the bell curve on height/weight, no allergies, no issues, perfect eyes, etc.
Trying to force the paleo diet on this crowd would be a disaster, so we each do something that works for us. My son probably eats more processed foods than he needs to, but his level of activity is very high and it all gets burned off. That is about the only change I would make.
This is an interesting and somewhat confusing experience for me, and does go to demonstrate that the Paleo diet simply isn't for everyone. With a few billion people on the planet, I don't think there's any way that one diet works for everyone.