It’s kind of funny timing. I was just watching the video from my wedding last week, and we had people stand up to give speeches. It was a little loosey-goosey since we had given warning to a couple of people. A few others said something, too.
It was a bit more formal than reception speeches. Basically, they were all serious—about marriage and about relationships and how hard they are and about the bridal couple and serious positive wishes for them.
Reception speeches tend to have more jokes. People tell funny stories about one or the other of the couple, or of both, depending on how well they know them.
If I were you, I would talk about the best qualities of your brother, as you know them. I would talk about what he will bring to the marriage, and I would offer my blessing to my brother, both personally (you’re there to help him) and in general, as a a member of the community that supports the marriage and will give the help you can in order to keep the marriage together.
Marriage is a difficult thing. Often times, couples can’t do it on their own. The more support they have from the community, the better chance they have. In particular, I would promise to listen to anything and never judge my brother. Never. I believe that if people had others who would help them without judging the things they do, there would be a lot more marriages that manage to stay together. But most people are afraid to talk because there is so much shame in having a marriage that isn’t working. If you could offer that to your brother in a sincere way, I think you would be giving him a gift bigger than almost anything else he ever got from anyone.