Join Date: Aug 2006
Location: Lake Gaston, N.C.
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You can't tell by the size of the parents alone. The Havanese breed has no doubt the largest genetic diversity of any "purebred" breed, so something can come out from several generations back. One dog three generations back, who was known for not throwing a consistent size, can still put a lot of variety in a litter.
When I read the title of your thread, I was going to come on and say you can't always tell final size from any size difference from birth to 3 or 4 months. We've had the largest in a litter from birth to 3 months not end up being the largest in a litter.
But at 9 pounds at 13 weeks, I'd bet he's going to be a big boy.
Bone size can matter too. A puppy with heavy bones can end up weighing more, but still not get too tall. The heavy bones will carry more muscle.
I just went and weighed the almost 12 and 13 week old puppies we have here that haven't been picked up yet. The fairly large boned 12 week old weighs 6 3/4 lbs., and the almost 13 week old fairly average boned one, weighs not quite 7 pounds. Both are very muscular from exercise at playtime and are in very good body condition. We expect the average boned one to be not over 12 pounds as an adult, and the larger boned boy probably close to 13 pounds.