just a quick simple question

Question
just a quick simple question  I have 2 cats one everyone says she is the runt of the litter.. She is super slender and just over all a very tiny frame just barely 6 lbs  she is just under a year old.. All up to date on shots and fixed the vet has never shown any concern.. Her sister was always a very strong athletic build she has become very stocky.  Just 9-10lbs
  They both eat the funny part is I always see the thin one more then any of them.  Theres always food in there bowl we feed them 2 times a day.  But they eat all day not all at that sitting..  How can I fatten up the other one and keep the bigger one under control as I do not want her to get any bigger.
Any ideas


Answer
There are some small framed cats.  That is genetic. It does not mean that the smaller cat is abnormal.  YOU can add oil, like corn oil to the food to add calories.

I am 6'5" tall and I weigh 280 lbs.  I have an older sister that is 5' 2" tall and weighs 110 lbs soaking wet.  We have the same parents. Does that make her abnormal? (or me?)