That is what we did. We didn't want the senior kitten to teach the new kittens any bad habits that he learned. Hopefully your remaining kitten stays healthy, doesn't get injured, and stays around for many more years!

So sorry for your loss. A couple of years ago our last of 5 cats that we rescued passed away at 19 years old. Now we have two beautiful ragdoll kittens (2 years old) that we adore and trained them to do tricks such as high 5's and turns.