My Pebbles (she's about 5 pounds) gave birth in August .... one of the pups which I kept (my Bitsy).... will only grow to about 3 to 3 1/2 pounds .. The sire (my Rocky) is only 3 pounds. All the other pups will be about 4 to 5 1/2 pounds full grown.
According to your comment nobody should have purchased my Bitsy!!!
Larger females do give birth to tinier pups (based on sire and/or genetics).
Let's face it, alot of us do have tiny yorkies!!!