I have a question and I hope this doesn't sound insensitive, because I don't mean it to be. My soon-to-be brother-in-law is 17 years old and has Down Syndrome. He could be a lot more mature, but his parents let him play video games for hours instead of teaching him manners and social skills. My parents recently met him for the first time and were appalled at his lack of manners. Not only could he not sit through brunch at my and my fiancé's home for more than a half hour, but he was belching and talking with food in his mouth (and his parents did nothing about it). He then played on the iPad, which was turned up to the highest volume (it would have been another thing if he could at least sit quietly).
Now I'm worried about what will happen at the wedding (June 2015!). To me, that behavior is appalling and having Down Syndrome is not an excuse for a lack of manners. What I don't know is how to approach the topic with my fiancé, especially when his own parents don't seem to care that their son has no manners. I want us both to be able to enjoy our wedding day, and I know my fiancé wants to have his brother there, but I don't want someone being rude or ruining the day for me.
Help!