Another Alphabet-Obsessed Child?

We played outside today, a beautiful and sunny afternoon. Erik was still playing on the slip-n-slide, and Anders was on the porch, wanting to go inside. He was whining a bit, when suddenly Erik started singing the alphabet song. "abcdefg..." Anders stopped whining, stood still, and listened. After Erik finished singing, I sang the song again. "....hijklmnop...." Then I went back to my book, Erik back to his playing. And suddenly, from the porch, came "...qrstuv..." OK, not in so many words. But Anders was sitting down and singing. He was so proud of himself, and it was so cute to hear him trying to sing a song he probably hears more than most 1-year-olds, as it's still a favorite of Erik's. It's the first time I've heard him really try to sing a song, however. So, is it familiarity? Or another letter-lover? Time will tell! " ...wxyz!"