If you have a postal scale you can weigh the kitten yourself.

However, this young, and not latching, could indicate a problem. At least CALL the vet. If the newborn is not getting sufficient nourishment it's SUFFERING.

You could get some KMR from the pet store to supplement the little one (and a tiny nursing bottle). But you might end up completely feeding it if it stops nursing completely. This can take up some time. The KMR isn't too expensive in the beginning, but as the kitten takes more, it costs more, obviously. Is this one as active as the other? Have you watched it nurse? Can you tell when the stronger one is full by its tummy? If so, check the other to see if it seems full.

Just some ideas. I nursed 3 kitties many years ago.

Hereball, thank you. I am on top of this.
Socks, I once raised a kitty whose mother died so I'm not new to this. We bought some KRM, can't get smaller one or for that matter, larger one to drink it. We have seen it nurse from mother and can hear the sucking noise. Just like what you mentioned,if I can successfully bottle nurse it may stop nursing completely and I prefer not to have that happen. I'll just give the rest of KMR to the mother. This one may just be a runt, I don't know but I am keeping close watch, the box is located near all of our bedrooms. I appreciate your reply. I guess at this point, it's just a watch and see situation. I am not as freaked out as I was.

Thank you,
Carla

Hereball, thank you. I am on top of this.
Socks, I once raised a kitty whose mother died so I'm not new to this. We bought some KRM, can't get smaller one or for that matter, larger one to drink it. We have seen it nurse from mother and can hear the sucking noise. Just like what you mentioned,if I can successfully bottle nurse it may stop nursing completely and I prefer not to have that happen. I'll just give the rest of KMR to the mother. This one may just be a runt, I don't know but I am keeping close watch, the box is located near all of our bedrooms. I appreciate your reply. I guess at this point, it's just a watch and see situation. I am not as freaked out as I was.

Thank you,
Carla

Maybe the little one will catch up later. If you're observing successful nursing I think it should be okay. I haul in feral kits for taming and often find one significatnly smaller than the others. They're all about the same by the time they reach 8 weeks.