Wish me luck (and advice) -- new kitty

Three days ago a very sick stray showed up at work. I took her to the vet and she only weighed four pounds, had a fever, bleeding from her vulva, bad case of fleas and severly dehyrdated and starving. It turns out she was pregnant with kittens and miscarried them sometime in the last five days. The vet said she was near the brink of death and that I saved her. It is very cold here in Michigan and he said she would not have lasted the weekend. She is a siamese mix (flame point) with beautiful blue eyes and is extremely loving. Now that she is on the road to health, I am petrified about introducing her to my resident cats. My two feline kids are 15 and 16.5 years old. The female is healthy but very much an alpha kitty. She doesn't like her big brother who is unfortunately on steroids for irritable bowel and takes thyroid medication too. He often times has bowel movements outside and has lost some weight. He still plays, wants loving and is eating well. The new kitty will have her own room for a few weeks. I plan on introducing them slowly. But I am overcome with guilt over bringing in a new girl to my old guys. I am glad I saved her life, but I truly hope I am doing the right thing.

Advice is welcome on how to alleviate potential problems. Wish me luck!!

First of all thank you for saving this dear kitty! Hopefully you older kitties will accept her. I don't have much advise on introducing new kitties but there are a lot of people with a lot of experience with that sort of thing here! Good Luck!

It is such a rewarding thing to do, to rescue a desperately sick cat. I can only say well done and good luck - I hope you manage to maintain a happy family all round.