Depends on the male. Some are jerks and others are lovers.

My males love babies. If he has been around babies and is sweet to them, you could get a young black male. If he is in with any of his sons at the store, that would be ideal. But it should be fine with any younger male if he is not a jerk. If he is going to be mean, you will see it within the first few minutes and separate. Different litters will be fine, little rats get along like little kids.

Again, depends on his personality.