Our yorksters are not really related, but we refer to them as brother and sister

. The one with the silvery head is Gatsby and he is almost 2 y.o. The one with the tan head is Daisy, she is 2 years older than her brother.
Thanks for the comments. They both are our wonderful pets. I love it when they entertain themselves like this, as particularly Mr. J Gatsby can play fetch, seeminly for hours, without getting tired of it! The humans, however, do tend to want to move onto other activities.