When I was a kid, my crazy aunt hated it when I had friends over. She would almost always tell me to go outside and play with them when they came to call on me. On those rare occasions when they were allowed to come in and play, she did everything she could to convince us to leave (vacuuming around where we were playing, etc).

When I was about eleven, I had a big fight with my friends, three sisters from next door but one, because they were complaining that I always came over to their house to hang out and watch television (we didn't have cable) and--get this!--their parents were tired of me being around all the time.

We never played together after that--in fact, they pranked my house on Halloween and would often call me rude names when they saw me in the street--and I was a pretty lonely kid for a very long time.

Considering Devon's mom's actions towards you, it seems not just possible, but likely, that his mom is not a very nice person. It's possible that Devon feels more comfortable in your home than he does in his own, the way I did at my friends' next door, which is why he eats all the snacks, etc.

That having been said, obviously Charlie's needs are important and should be paramount to you, as you are his mother. But, although I could be totally wrong, it sounds like this other kid could use some mothering too.