I remember when picking out Koda, Allie and Kammie how their feet/bone structure played part. In the way they have grown in relation to the bone structure has pretty much been right on. Koda was bigger boned, and now at 15 mos he is right under 7lbs. Allie's structure was super tiny, and when we lost her
at 6mos she only weighed 2.5lbs. Kammie was a midline structure compared to her siblings and she is a little over 5lbs at 8mos. So I personally do think their bone structure in their feet play a part in what their size will be as they get older. Mind you, this is just coming from our personal experience, not science based, lol!
