He was a friend of Liszt (indeed, it has been suggested that he was an illegitimate child of Liszt's!)
Wait, was he the son of Agnes Street née Klindworth? There's a whole chapter on his mother in the 2nd volume (The Weimar Years) with some brief mention of her son, yes, including refutation of the claim that he could possibly have been a son of Liszt's - the dates just don't work out. But his mother was a very interesting person indeed, spy, confidante, ... that chapter makes for very
And if memory serves- I think I've misplaced my copy too - he (her son, Joseph) helped Bizet's Carmen reach the stage, or something like... His father's name, if I remember, was Denis.
Except according to the Google-able copy of the Weimar years, Agnes' sons were Charles and George, not Joseph - so the answer to my question is no, we're not talking about George Street here. (I would add that the dates for Joseph Street are supposedly 1800-1880 - preceding Agnes' birthdate of 1825 by some time - but I have no clue where those dates on IMSLP come from - will try to find out. He is not, I think, listed in our 'usual sources' - musicsack and viaf.org being the two most often consulted by me now anyway... and when those come up empty, as they do eg for Percy Hilder Miles, it often seems wise to at least put in where one's obtained one's information (as I tried to do when starting a Wikipedia stub for the latter) - anyway.)