I live with one ham stealing cat (see previous threads) and we are very happy. He is big softie who is very loyal, sleeps on the bed and brings gifts back to the house.
However, I think I am being adopted by a ginger tom who comes to our house and yowls to be let in. A friendly cat who always turns up when the weather is foul and cold. I don't feed or let him in but he is always there.
Yesterday I opened my back door and this ginger cat shot into the house and ran up the stairs and hid under the bed. My cat had a big hairy spit at him and eventually I shooed the ginger out of the house.
Now my cat is vomiting on the rugs and looking nervous, not eating and staying inside whle ginger sits outside, making eyes at me throw the windows.
I feel sorry for ginger but don't think I can have two. But its as if he has decided hat he's going to be here, hell or high water, and my lovely cat has dissolved from a lovely chap to a sicky nervous beast.
Have you asked around the neighbours to see if anyone knows anything about the ginger cat? Does he look well fed? Is he neutered? I think the first thing I would do is put notes round the neighbours to see if he belongs to anyone. If you get no response then I would catch him (which sounds as if it would be very easy) and take him along to a vet or cat charity for them to scan him to see if he has a microchip (vets should do it for free). If he doesn't, then I would think about contacting your local cat rescue (check that it has a non-destruction policy and don't go near the RSPCA) to see if they can take him in. He is obviously desperate for a home and its a shame for him to be stray.