"Kateřina, why did you marry František?"
Translation:Kateřino, proč sis brala Františka?
Thanks, it's an interesting article that thoroughly documents how these forms flucuated throughout our history and how different linguists had different attitutes towards them.
However, today, "ses" and "sis" are officially the only accepted forms of combining the reflexive pronouns "se" and "si" with the 2nd person singular form of the verb "být", while "jsi se" and "jsi si" are incorrect according to the official code: https://prirucka.ujc.cas.cz/?id=580
I sometimes catch myself saying "jsi se" or "jsi si", probably because I'm from Prague, but I would never write it. And reading it hurts my eyes. :-D