They are sort of related, though: both trace their origins back to famous study by TsAGI in early 1950's, which spawned three important lineages: MiG-21, Su-9 and Su-7. Something like 20 000 jets were built based around those concepts.
Regarding J-8, this was asked already, but does anyone know about early J-8 production numbers: English and Chinese wikipedias state that basic version was accepted to service in 1980, and production terminated in 1985, but no other details are given. Regarding J-8I, English wikipedia claims that 'around 100' were built, while Chinese wiki puts the number on lowly 31. As it was in production only for couple of years, smaller number sounds more credible.