4 Months Old!! I still can't believe its been 4 months yet there are days that feel like it has been a year...At the last checkup, Jaxson weighed 12 lbs 2 oz while David was 13 lbs 15 oz. Funny enough head size and length were the same. We are now wearing 3-6 months clothes for everything, even socks! They continue to grow so quickly.