Kitten Not Growing

My son brought home a 6 week old kitten, from one of his friends litters.  He (Oliver) is now 10 weeks, and still hasn't grown.  He is always hungry, he acts like he never eats, climbs up legs just to get to food.  I started him on wet food, because the kitten food was really hard for him to chew.  He woofs it down so fast.  He has a tummy, but he just isn't growing.  I can't even give him his first shot because there is no extra skin for it to be subdural.  I call him my little midget, he is the youngest of 6 cats.  Bella is just 3 weeks older than him and she is 2 1/2 times bigger than he.  He is sassy, plays hard with Bella, cuddles up to Milo, while Milo loves on him.  He just isn't growing.  Is something wrong with him? I suspect he could possibly be the runt, but shouldnt he have grown a little bit in the 4 weeks?

robin

The general rule with kittens is they gain a pound a month. This is specifically true for the first 5 months or so.

Has Oliver had a wellness check-up at the vet? If not, that is where I would start. He certainly doesn't have to get vaccines at the visit. But, a good thorough check over is needed.

I would also invest in a digital kitchen scale (that weighs in ounces) and weigh him on a weekly basis.

It's certainly possible that he could have an absorption disorder, though that is usually accompanied by diarrhea.