The link is actually reasonably well known but commonly exaggerated - Neil Bush (son of George and brother of George W.) was an acquaintance of Scott Hinckley, John Hinckley's brother. Conspiracy theorists have come up with a lot of closer links, but without any real evidence for them.
But they have at their core 'members of the Bush family and members of the Hinckley family knew each other' and that is technically true.
I don't have time to go and find an accurate link that isn't full of conspiracy additions (that's the big problem - finding links that discuss the connection is easy, but wading through them all to see which are accurate would take time).
Highland Park in Texas, is a pretty exclusive area. A good friend of mine went to school in HP at the same time as Hinckley (they were even on the same middle school football team) by the logic of the conspiracy folks he may have been involved!
LOL