When my boys were born Byron was 7lb15oz and Miles was 8lb 2oz. Miles fattened up faster and got almost 1lb heavier than Byron but once they started solids (9-10 months) Byron started passing up Miles. Miles was way more into solids and not as into bfing and Byron still pretty much only nursed so I guess that made Byron gain weight faster. Now at 18 months Byron is 28lb 8oz and Miles is 27lb.