YOWAPEDA SPOILERS. (Spoilers if you only follow the anime and english scanlations. Otherwise, it’s trivia) Friend on twitter asked me if Makishima’s brother being a fashion designer or not was a headcanon, and then things exploded. www
Source is from a friendly twitter who gathered up all the info that Watanabe-sensei talked at an autograph session about the characters. You can view here. If you also browse through the #pedal night hashtag on twitter, you’ll see lots of other stuff!
Since the info is from twitter, a warning that there may be mistakes, and Watanabe-sensei may choose to change his ideas in the future! So nothing is really set in stone.
Bold parts updated 08/09/14! My comments in ((double parentheses))