Both my yorkies have parents of simular size to yours, they both weighed 3lbs until about 7 or 8 months then they hit a growth spurt. Missy is now 10mo and at the last vet appt. she weighed 4lbs 10oz and Max is 8mo old and weighed 4lbs 8oz. They are both really close to 5lbs now. I am in touch with someone who has Max's brother and she said his brother weighs 7lbs at 8mo and my sister bought Missy's sister and she only weighs 3lbs 8oz.
Soooo... you never know. My guess would be your pup should be a little under 5lbs but you'll have to wait and see.
