Finger/Thumb sucking

I have childhood memories of classmates sucking their thumb but don't remember any of them having a pacifier.  I've also heard the saying "you can't cut off a thumb" and have been warned about the dental problems thumb sucking causes. 
So, I registered for multiple pacifiers. Before Brex arrived, 23 different pacifiers were washed and waiting for him. He takes them occasionally, but he much prefers to suck his thumb or fingers.

He's not even picky, any finger or thumb will do just fine...

Brex sucking his own thumb:

Brex sucking his pretend brother's thumb:

Brex sucking his own fingers:

  

Brex sucking his pretend brother's fingers: