I have two cats male and female, they are brother and sister and are three yrs old. The male who is a big boy is very playful where the female who still resembles a kitten herself is much more reserved and sits up high out the way of her bonkers brother. I have found a kitten of 8 weeks that needs rescuing and am worried about how the other two will take to her? Both the older cats are living they have never fought with one another (only play fight) I'm worried that this kitten could get hurt? Can someone advise me am I doing the right thing?

Loving not living... typo x

You should be fine if you take it easy.
You'll need to have a separate area for the kitten and allow the other cats to interact on their own terms. Don't force anything.

We've recently introduced a kitten to a group of 4 other older cats and they are starting to come round, but it's taken a week or two for this to happen..
Lots of hissing to start until they have all realised that there's no threat involved.