As with many situations, it depends on the individual kids.
I got my first yorkie puppy when my kids were 3 & 5 years old. They loved growing up with a tiny dog. That yorkie has since passed away and both the kids are now in college. They bought me a new yorkie puppy in January. My son was just home on spring break last week and the 6'3" hockey playing tough guy spent most of his free time snuggling with the new pup...he still loves tiny dogs
