Jennifer,

I'm going through the exact opposite with my two kids. My son is average and my daughter is malnourished. Two kids in the same house getting fed the same food. My daughter gets picked on for being small and under developed. She eats all the time too, but she doesn't gain.

Try not to point blame. Your sister is probably beating herself about it just fine.

Another thing - the kids next door had always been heavy until the last year or so. They both shot up in height and grew into their weight.

I'd say be supportive, don't point fingers, have healthy snacks available for her. Once my daughter found out from the doctor what she needs to do to get healthy, she really took a interest in what she eats. Hopefully the same will happen for Kate.