My older girl Zoe' weighs 10 to 10 1/2 pounds and she is 2 years old. Her mom weighed 6 to 7 pounds and her dad weighed 4 to 5 pounds. Everyone told me to double her weight at 16 weeks which is about 4 months. She weighed 4 pounds and 2 ounces then. I would guess yours will probably be in the 8-10 pound range.
You just have to kinda wait and see though. Like everyone says there is no way to really predict.
Telea, Zoe' and Mia