Separate the males from the females for at least one night before you introduce to minimize the chance that they smell like females.
Get a nice big well ventilated cage, clean it well, and put all 3 in the cage. They will be so excited over a new clean cage, new smells, and other new guys they generally won't tussle at all.
As to socializing, that's something you have to work on when they are young. From the weanling size I start handling them, playing with them, giving them treats. They learn in just a few sessions that you aren't going to hurt them, and in fact bring them treats!
You can try to socialize adults, the best bet is to use food as a motivating factor. They loOOOOOOOve sweet treats. Don't bother to do this with nursing mothers, as they are already protective and if they try to bite, will still try it.
The chances are slim that they'll take to you, but some of them very well may. Don't hold back any offspring from the ones that bite you. It is pretty inheritable. You'll want to focus on the outgoing rats that are healthy and robust.
I like to single out the animals I want to work with and have single sessions with them. We just sit in the living room and chill. I usually get it to work after only 3 sessions of this one on one. Hoodies are especially useful to be wearing during this.
Also, rats that are really playful and outgoing sort of rub off on the other shy ones. I like to put the skiddish and shy ones in with the rats that practically jump out to me.
I've only had a rat singled out when he was sick. He was mopey, lethargic, his fur was looking dingy and unkept. It's like they just lose interest in the world and will start to decline in health.