Just because you lost, don't feel bad. Really. It's not all that important. I used to play smash with my [little] brother all the time, but we stopped for a long time because I would always beat him. As the older brother, it made me sad I couldn't play vs my little brother anymore.
If he's older than you, he basically has an unfair advantage. You will have to practice more and try really hard to be better than him or as good as him. But really, as brothers I think it's more important to just have fun together. Maybe ask if he wants to do 2v2 vs computers or 2v1 to practice some team combos vs a computer.