I guess I'm thinking along the lines of that they are divorced already....even though they are not. I think it is unreasonable to think that your divorced husband would give you a birthday party. If I left my husband I would think it was VERY strange that he got me a cake and sang happy birthday with my son. I wouldn't think it was odd if he "helped" him get me a card and small gift, however. That's it, though. It would be like he was pretending we were a family when we weren't.
