Jack-Jack Attack

I am starting to wonder where, exactly, Jackson came from. More specifically - his temperament. He has always been his own person - independent to a fault & very opinionated. He is an (almost) polar opposite of Daniel at the same age. Perhaps it is partially because he is the little brother (but I doubt it).
Example 1: Sign Language
I have been attempting to teach Jack the basic signs that Daniel knew (and used) at his age. He went along with me for a while, but now refuses to use them. I know he understands the signs (such as hungry, more & please), he just flat-out refuses to communicate with his hands. I think it is partially because he can see that Dan communicates by speaking & he wants to do the same. His speech is developing, but not nearly as fast as he would like, so most days it boils down to grunts, screams & thumb-sucking.
Example 2: The Blanket
Jackson has tried to adopt a "lovey." Two blankets in particular are his favorites. One we had to hide (trying to curb the attachment issues), the other we were successful in leaving in his crib after he woke up (out of reach). If he does by chance get a hold on one of these two blankets, he will throw a royal tantrum once it is extracted from his tight little fists. Complete with screaming, crying, kicking & standing in a corner (all of his own accord.)
I really don't know where he gets it from. Any advice on dealing with our strong-willed child is welcome.