I have two cats indoors. A stray cat appeared at my house 2-3 months ago. It took me a couple of weeks before it would let me pet it. I have been feeding it, gave it a bed inside my screened in deck. I'm concerned about winter coming. I would like to bring it in the house, but it hisses and claws at my other two house cats so I don't let it in? How do I handle this and what do I do?