I get asked a lot how similar and different Thing 1 and Thing 2 are. The answer: it changes. A lot.
Not very specific, I know.
As a general rule, Thing 2 is much more emotional. He's more of a cuddler. More of a mama's boy. He is incredibly sweet and thoughtful, but a lot of times this is only when it suits him. For example, he will steal a toy from his brother, and then when brother starts crying, Thing 2 will run and go grab a different toy--one that he doesn't want--and hand that to Thing 1 to soothe him. Thing 2 can also turn on the waterworks and throw fits like you would not imagine. Everything is the end of the world--a toy being stolen, someone looking at him, getting his diaper changed. He's a bit of a Drama King. He's also the chattier of the two. Thing 2 talks all day long (not that I can understand most of what he says). All in all, I'm afraid most of Thing 2's personality comes from me. Poor kid!
Thing 1 is definitely the older brother. You wouldn't think two minutes would make a difference, but it so does. Despite being a tiny bit shorter and like two pounds lighter (that's a lot when you're a toddler), Thing 1 can drag Thing 2 to the ground and show him who's boss. And he does so frequently. He's been biting the heck out of Thing 2 lately (poor guy), leaving welts all over him. In Thing 1's defense, he's teething. Anyway. Thing 1 is the more stubborn and independent of the two. He is usually much too busy to cuddle, although both of them love giving air kisses. He also has a stubborn streak like you wouldn't believe (also my fault). Where Thing 2 gets more sad and cries during temper tantrums, Thing 1 has definite mad cries. He also is more of an observer. He likes to sit back and watch Thing 2 make all the mistakes so he can learn from them, and then when he does something, he perfects it. Like Thing 2 was attempting to walk long before Thing 1, but when Thing 1 started walking he did so without many hiccups. He's doing the same thing with talking right now. He talks significantly less than Thing 2, but he soaks it all in and when he does start saying a word, it's usually clearer. Thing 1 is more analytical. He likes to try and put things together, figure out how they work, etc., where Thing 2 just wants to play and have fun.
However, that being said about my sons...they have been known to switch personalities on me for a few days without warning. Suddenly Thing 1 will be the emotional one, and Thing 2 is totally fine. Just when I think I have them figured out, they switch. They're learning that if they work together, the can confuse mommy and usually outsmart her. :)
My kids are different enough, though, that I can usually tell them apart by just their cries. They just sound different, and I think a lot of that has to do with their personality.
Thing 1 and Thing 2 may look the same, but they are definitely their own distinct little people with their own personalities. I wouldn't have it any other way.
TWIN MOM TIP: Try not to worry if your twins aren't doing the exact same thing, at the exact same time, especially developmentally. Keep in close touch with their pediatrician if you're concerned, but remember--they're two different people, and they will learn and grow at different rates.