Definitely sounds like she feels her kittens are not safe where they are, and even neutered males can have problems socializing with kittens. How old was your male when he was neutered? When we've had litters, we normally keep all except the 'mamas' (sometimes 2 have litters close together, timewise), away from the other cats until the kittens are around 6 weeks old, and venturing out on their own. By then, they often show tendencies toward bravery, or desire to not be as explorative. Those who want to be out on their own more are introduced very carefully to each of our other cats. If I had one who appeared to be a danger to the kitten(s), I would definitely keep that one separated from all of them until they're old enough to be accepted and defend themselves better.
Also, by the time they're 4 weeks old, ours begin having their nails clipped each week, and get used to being brushed. It's also a good time to get them accustomed to having you check their eyes, ears and teeth.
Good luck with your babies!
