After a couple of email exchanges with Mother-of-my-Children (some of which were heated), I have a better idea of what Oldest Son was talking about regarding staying at my house on Sunday evenings. I had been concerned that there might be something inappropriate with MomC pushing things on Oldest. But now that I have the full story, I'm confident that there is not.
The crucial bit of information was that she suggested it because he told her he wanted to be able to spend more time with me. Oldest told me that she had suggested it, but left out the context that he had been talking to her about spending more time with me. It's fairly common for Oldest to leave out important information when he tells you something.
Last year was the first time he started having to do homework. Previously we'd had his IEPs written in such a way that he was exempted from homework. I would ask if he homework was done, and he'd say yes. Then I'd find out later that his homework wasn't all getting done. I eventually figured out that when he said his homework was done, what that really meant was he was done with all the homework where A) he knew exactly what tasks had been assigned, and B) he understood how to do the work. If he was unclear exactly what the assignment was or he didn't know how to do the math problems, he didn't mention that.
I remember an article I read years ago about adults with Asperger's Syndrome and they trials they run into communicating with other people. It talked about a young man who was having trouble finding a job. His previous job had been cleaning rooms at a ski resort. It was seasonal work--the job ended when ski season was over. When he was interviewing, he told people that he had been "let go" from his previous job. He didn't realize that this sounded like he had been fired. He didn't understand that he needed to provide the context.
Which is exactly what Oldest did. He told the factual truth, but without the crucial contextual details needed for me to understand what was really going on.