Welcome, Heather!! You're braver than I ... don't think I could handle two!
Our Toto is 16 months and 4 lbs. of neverending energy! She was 16 weeks when we bought her and she weighed 1 lb. 8 ozs. ... I know they have a "rule of thumb" to try and estimate weight but I'm not sure what it is! One thing I am certain of ... regardless of the estimates and expectations, you are so attached after 5 minutes with these babies, there is nothing that could pry them away from you!!
Looking forward to hearing about your babies!!