One Kitten Smaller Than the Other?

Hi,

Last week I took in two kittens from the same litter -- a brother and a sister.  But even though they are litter mates, the brother (Pepper) is larger than his sister (Pickles). I had them vet-checked last week where they were checked and treated for worms.  Even the vet commented that Pickles was a little on the small side but she seemed healthy (clear eyes, nose and good coat).  It's just whenever I'm petting them I can feel how slight she is compared to Pepper.

She eats well -- she'll even push Pepper out of his own dish from time to time (they have separate dishes).   She is definitely the more timid one but can hold her own in kitten scrapping and she is very energetic.  Poop and pee seems normal.  I'm scooping twice a day so I think I'd notice if something were up.

Is it possible that she's just naturally smaller than her brother?  I am keeping an eye on it but don't want to rush to the vet for every panic.  I'm feeding them Performatrin Ultra Grain-Free Kitten dry formula, if that makes a difference.  Is there something I could give her to put on some weight?

Thanks.

Just wanted to add that I have two small children (4 and 1) and they are still overly enthused about having new kittens so is it possible they are stressing her out a bit?  I know I lose weight when I"m stressed even if I'm eating OK.

It's very common for female kittens to be a bit smaller than males; besides, any two kittens even in the same litter can be different sizes and be perfectly normal. If everything else seems normal I wouldn't worry about the size difference.

Do you have a kitchen or baby scale you can use to weigh her? That would let you track her weight gain and ease your mind, or show you if there really is a problem. Kittens typically gain about 1 lb per month, though it can be a bit more for boys and a bit less for girls.

Thanks.  I don't have a kitchen scale but will look into getting one (need to watch what I'm eating anyways, ha ha)  She is also a bit more bony than her brother but nothing alarming.  It's not a visible difference, for instance.

So, bit of an update:

Pickles is still smaller than her brother.  It's fairly noticeable too.  He seems to be filling out and turning into a little "man cat" already and she is just so slight and small.  You can tell she is growing and she's definitely not emaciated but I sometimes worry she's a bit too bony.  There is fat on her ribs but her shoulder blades feel a little too prominent for me.  She is still as playful and alert as always and can keep up with her brother.  Pepper is also fluffier than her but their dad has longer fur while the mother is a shorthair so it could simply be genetics there.

Anyways, right now my running theory is Pickles isn't crazy about the kibble I'm feeding them and only eats enough to sustain herself.  Her eating style also is to eat smaller portions more frequently.  But Pepper is like a little vaccum cleaner and hoovers everything down and I think he eats her portions sometimes.  I have seperate dishes for them but they both insist on sharing no matter how many times I separate them. 

Today I picked up a can or two of Friskies wet food (can't get to the premium pet food store until tomorrow) and she gobbled up her portion pretty quick but, once again, ate much slower than her brother and he came and ate the last few bites of hers.  

Any tips on how to make sure Pickles gets her share or how I can put more weight on her?  I plan on feeding her more wet than dry from now on (Pepper is thriving off the grain-free kibble I'm feeding him).   The kittens are almost always together so it's tricky feeding her on her own.