I got 3 of my girls at close to a year old and they all grew until they were about 1 1/2.

Angel was 3.5 lbs. at a year old and she is now 6 lbs.

Candy was 2.75 lbs. at 11 months ...she is now a year and 4.3 lbs. She isn't finished growing yet.
Princess was 2.5 lbs. at a year old. She is now almost 3 lbs.
We won't talk about Kissy
If you had her spayed, she will probably gain a little weight too!

Just think...the sisters will be able to share all their clothes this way!!