We had a similar "shock" with Brew.
Mom was 6lbs and dad was 4lbs.
we got him at 8 weeks (i know now thats eeek...but i found yorkie talk after
) he was 2lbs then. He gained a pound every 2-4 weeks and he is now 9.2 lbs at 7 1/2 months old. he has really slowed down on growing though and he's been pretty steady at that weight for about a month now.
not to say that your sweetie will get that big, but just to show that the parents don't always give a look to the future.
i had a 3.6lb yorkiepoo who lived past 14 years old and i must say it's MUCH less stressfull having a more robust pup around.
he still sits/fits in my lap!! and it's just all the more Yorkie to love
