Keep the Mr Raggs seperate from your cats is the right thing to do BUT is it fair on Mr Raggs to spend the rest of his life alone ?

Why do you want to keep him so badly ?

What is best for Mr Raggs ?

: Living elsewhere with the run of a house, with other FIV kitties

: Living in your spare room on his own for years.

You need to stop thinking about what you want and start thinking about Mr Raggs. He could be a perfect companion for an already infected cat.

There are plenty of healthy cats you could adopt which could be mixed in with yours, if you are looking for another pet right now.

Alternatively you can wait until your current cats have crossed the bridge and fill your house with FIV kitties (Which would be a very loving & charitable deed)

But can you put your hand on your heart and say that living alone in one room for life is the best possible life for Mr Raggs.

PS. He is a very bonnie cat and I bet he could relatively be very easy to rehome.