Well this is my very first Bleach theory! I was thinking about the “rescue Rukia” arc and what we learned in it about Yoruichi (who btw is so great) –namely that she is the princess of the Shihouin family. Throughout the story we also saw that the Shihouin family have lots of special and powerful artefacts. But what we also know is that Urahara Kisuke is the greatest genius ever and the inventor of countless revolutionary devices and methods. So I think there’s a connection there. Kisuke grew up with Yoruichi and became the greatest inventor and Yoruichi’s family just happens to have a lot of amazing artefacts and I don’t think this is a coincidence. Yoruichi was a princess of a family at least equal to the Kuchikis so she probably wouldn’t have been allowed to associate with just anyone just like Byakuya wasn’t allowed to marry a commoner. So I believe that the Urahara family is one that served Shihouin –specifically in the realm of creating devices for them. This explains where Shihouin got so many artefacts and also how Urahara and Yoruichi met and became friends. It also explains how Urahara discovered his genius and learned to build so many wonderful things. He’s not a member of a noble family or one that has other Shinigamis but he certainly seems to be a member of a family as he didn’t take his name from a district like many other characters did. I don’t think that the particular artefacts of Shihouin were created by Urahara because his inventions tend to have his name attached to them instead but rather by his family over time. They probably all have the aptitude for it but just like Yoruichi is the strongest Shihouin and Byakuya is the strongest Kuchiki Kisuke is the smartest Urahara ever. Kubo seems to like family legacies so this would be up his street. Ooh, I wish we had a Yoruichi smilie!