Originally Posted by Katelyn'sM om
I'm shocked by the description of the other children. By 4 their speech should be clear.

Heh. My niece, who was the tiny-child-reading-Harry-Potter and the entering-kindergartner-doing-multiplication, was completely incomprehensible to everyone but immediate family at 4, and took quite a bit of close listening before your ears adjusted to the way she talked, but after that you could mostly get the gist of what she was saying, at 6.