I don't have a JRT, but do know of many people that do. Some can learn to live w/ them fine.

Since you already have a pup then yes you should get a kitty asap to help them learn to live w/ eachother.

It would probably be best to get a young kitten or at least one where you know the background of the cat & know it gets along w/ dogs just fine.

You can talk to your vet, obedience instructor & breeder on how to get them accustomed to each other easier.

good luck!