I keep two neutered males with three un-neutered females. I didn't rush the introductions but did it very gradually but now they all get on fine.

I agree with the last post. One of my females has recently had to have two lumps removed which may be cancer. She is really too old to have neutered but I will be having the other two done now I am aware how high the chances are of them getting cancer if they remain un-neutered.