
Soooo.... Nezuko never got together with Zinetsu??? Or im just blind ???

What? Yorichii isn't related to anyone. He died 400 before the series even started. Nezuko and Tanjiro are siblings, so if Yorichii was Tanjiro's brother, he would also be Nezuko's brother, so they can't get married before either way.
Nezuko married Zenitsu, Tanjiro married Kanao, now their great grandkids are dating.
What secret exactly??? That SHE IS A HE?! OR That he's pretending to be another person?! But seriously, whats more bigger issue than being tricked that he actually married a dude and they did the dirteh which i think he's fine with it!!! GET YOUR SHIT TOGETHER MAAAAN, MAKE up YOUR DAMN MINDヽ(`Д´)ノ
the prince already knew 'she' was actually a male though