Children, in the same family, are not the same. Parents compare. Before I had children and when I worked with parents, I was continually amazed and abashed at parents who compared their children ("His brother wasn't like that!"). Of course they were different! They may have shared some genetic material, but I couldn't fathom why any parent would expect similarities between their children.
Then I had a second child. She amazed me from the very start because, well, she wasn't really very much like her sister at all. I have thought about this in the nearly three years she has been around -- why do I imagine that there would be similarities? Well, one thing is that an experience like childbearing (and I mean this in the global pregnancy-birth-childrearing sense) is something we humans like to encode and form schemas around. We like to know what to expect and understand from our interaction with this tiny human. So, part of our schema is the child -- how s/he acts, looks, etc. So I think we may be 'hard-wired' to expect similarities.
Another thing that pushes us to believe the idea of sameness is that we often scan our children for similarities to relatives, living and dead. And of course they will be compared to siblings in this way.
So my second daughter showed me what stubborn was. She was that way from the start -- her cries were healthy and indignant when the breast wasn't whipped out fast enough, whereas her sister (sigh, comparison...) calmed the minute she saw me fumbling with my shirt and bra. Daughter two also had the most unusual fear from birth: she was afraid of the dark. I kid you not, she would wake in the middle of the night, a few days old, right next to me and HOWL until I got my little book light on (this was the first gadget she mastered at about 6 months of age). I have never heard, anecdotally or professionally, of a baby who showed fear of the dark. Interestingly, at nearly three years of age, she is over it.
Child two also has an amazing sense of logic. As she has learned to talk, you can see her in the mornings carefully parsing sentences and thinking carefully about how and what she wants to communicate. My husband took to counting the words in her sentences (wow! ten words! -- and I would have to correct him because it was 9, she had forgotten a preposition and he had implied it when counting... still... nine word sentences at just over age two... well... her sister never did that...).
Child two hasn't been as encumbered by the French language as her sister. When still a small baby, she would giggle when she heard me speak French (we speak English in the home, obvioulsy; we don't want our children mimicking our poor accents and grammar usage) -- big sister would cry when she heard me speak French (I was more tense back then when speaking French...). Child two has had an anglophone babysitter for two years and we recently replaced her with a Francopohone (who is on vacation and being replaced by, for all intents and purposes, another anglphone... another blog for another time). So she hasn't had as much direct contact with French, but she seems intrigued by learning it (she has been saying "Bonjour" and "Au revoir" as well as "Merci" for months now, when we go to stores and are out and about). She replays over and over the French dvds that her sister checks out of the mediathèque... it is like her own personal method for learning the language.
My brother who heard her on the phone recently commented that if adults would approach language learning like a two year-old, they would learn faster; he posited that their method consists in repeated trials and errors and that they eventually parse a sentence that makes sense, but the bottom line is that they try, doggedly, until they get it right, and don't care about making mistakes.
So this child has been learning language, but also so much more that is not as observable. Her keen sense of logic has pushed her to do and think about things in clever ways. Her sister is amazingly clever, but in other ways.
Child two, being around the age of two, likes to help on occasion, and welcomes the opportunities for the most part. Most recently, she has been gleefully putting down forks and knives at the dinner table for us. Last night, as she was parading around and announcing she wished to go out in the backyard, I asked her if she would set the table for me. She looked me, and in all seriousness said, "No, mommy, I want to go outside right now". I said, "I'd like to go outside too, but I need to cook dinner and get things ready for us to eat. I can't go outside." She replied with an even more serious, and perhaps regretful, tone, "Mommy, you are a big person. That is what you do. I am a little person, I want to go outside." Which she promptly did.