Re: New and need advice
Welcome to CatForum, ditto to what Hoof said and I hope we can help.
First, I think it would be in *both* of your cats' best interests if you isolate them for the birth and initial raising. Mother cats can be very quiet, easy-going and loving ... but after they give birth it seems like some hormone kicks on a survival instinct and there is a very high probability that she will become extremely aggressive about protecting her litter by attacking her brother to drive him away.
She will not be able to help doing that, instinct and hormones will be demanding of her to safeguard her litter at all costs.
So, keep a door closed between the adult cats. I have only had one litter born in my home as an adult, and only a very few born when I was a child at home, so I have very little practical experience. With my pregnant foster in 2004 I set her up in the bathroom with a large cat carrier, but ideally a 2'x2' box with a top and a hole cut for access/privacy would be roomy enough for her to maneuver around for birth and re-settling down with little danger of smothering a kitten in too-cramped quarters. I also like to use towels placed inside a pillowcase as bedding because the loops on towels can catch kitten claws and they get stuck, the smooth pillowcase prevents that.
Best of luck and I hope everything goes smoothly.