welcome to the forum and very sorry for the loss of your little one. It's wonderful that you are rescuing a little one as a friend for Kobe. I haven't really had a problem introducing a new fuzzbutt to the others, i recently brought a new addition home to my other two. They were a big grumbly and growely for a few days, but now the new little guy has two bestest buds. Just try to introduce them to each other calmly, and if possible on neutral territory.
that things go smoothly.