Last night the one-year-old spoke his first complete sentence!
We've been a little concerned about his speech. Because both of his older brothers have autism, he is part of a long-term tracking study of children with multiple siblings with autism. At his most recent evaluation, they said that his receptive language was extremely good (85th percentile), but his expressive language was quite poor (10th percentile). They recommended speech therapy.
He's been doing speech therapy for a month or two now. He works with the same speech therapist that worked with the eight-year-old. One of the things the speech therapist recommended was prompting him to repeat words and sounds frequently.
I've been making him tell me that he wants to get down from his high-chair after meals. Normally, he makes the sign for "all done." He's been using this sign for at least six months now (he is twenty months old).
Last night after dinner, he handed me his plate. He tried to stand up, but the tray of the high-chair was too snug for him to stand. I said to him "what do you say?" I was expecting him to sign. To my surprise, he looked at me and said "I'm all done."
I was so excited that after I got him out of his chair, I called my ex-wife to tell her about it.
So now his speech is something that I'm not as worried about.