To be honest I am afraid that a new cat could mean stress to Moritz and his illness could worsen faster......

Maybe you could foster a shelter cat and give it a try?

Yes, wonderful that at least one of the younger boys is close to Floppy, they all love and adore their older brother so much ! If I only knew that Moritz would be happy with new cat family members, too I would drive to the animal shelter immediately

Because of these dear cats, Floppy isn't alone, the last survivor of his family. They're with him ALL the time, doting over him, without fail. They're better than 98% of the humans I've known in 53 years, especially including myself.