He has great head control and wants to sit up to see everything but is obviously too young to sit by himself

but she had good neck control

This seat is perfect for the infant who has good head control but isn't sitting up by themselves yet.

and he's a big boy and has great head control

It says 4+ months but honestly as long as they have decent head control and you’re right there with

n’t have as much luck with the Bumbo seat