Most of the SBWII recordings, and all the well-known ones, ARE from much later than the SBWI recordings - but the men were contemporaries; however, SBWI was a "star" first. He was based in Chicago, or at least worked there a lot, while SBWII was still working in the South. SBWII took the name to cash in on it. They did meet sometime a few years into the mutual name business, when SBWI made a trip South, and apparently he bore SBWII no animosity, presumably feeling that SBWII was just doing what he could to get by, and it wasn't really hurting him. SBWI was clearly a major influence musically on SBWII, in his harmonica style but even moreso in his vocal style.

Although SBWI died in 1948, he wasn't a whole lot older than SBWII, who lived into the 1970's; he just ran into some bad luck.

I don't have any particular inside knowledge on any of this; I'm just repeating things I've read here and there ...