"Kateřina has many cousins."
Translation:Kateřina má mnoho bratranců.
I gave the answer Kateřina má mnoho bratrancy, and Duo approved it but claimed a typo as correct spelling is Kateřina má mnoho bratranců.
1) not sure why he considers this a typo when this is a mistake 2) does "mnoho" demand genitiv despite "mit" demanding accusative?
The system assumes one letter off as a typo, unless it creates another existing word (good vs. god). Bratrancy does not exist in any form so it took it as a typo.
You are correct with mnoho and genitive. I am so glad this is my native language so I do not have to learn this!