Hello, Yes they can, but somethings to consider. If the male is the minature, he might have some "connection" problems due to his height. If the female is the minature, you don't want the male JRT weighing more than 5-8 pounds over her weight. Big puppies in a minature can cause big problems, but with a VET assisting on the checkups and maybe an ultrasound, you should be just fine. Also, make sure your female is 2 years or older and your male 2 years or older. Kids shouldn't have kids---even in dogworld!
GOD bless you and your JRT's!