It all depends on the little in question!

As far is Sam is concerned, he is ultra protective, but the first thing Sam will do is scold him for not giving him space or independence. Dean tends to take stuff like that to heart, so he’ll lay off (a little), and Sam won’t feel so stifled.

Of course, if you don’t tell Dean right off, he tends to get in habits, and might end up just casually picking you up and taking you wherever he is, as Jacob can well attest to in certain future AUs. Sam would be the first to tell him he shouldn’t let Dean get set in his ways! 

As a little himself, he’s an incredibly fussy guy. He’ll lecture Sam for days if he gets himself picked on at school, and when Sam’s a smol Dean does his best to keep him away from danger. It’s a lot harder for the little guy, but he tries!