Ha! I thought it meant 'Can you see their parents' house?' :-)
"their" is jejich with a short i
I wrote "Do you see her parents' house?"
Duolingo suggested I had a typo and got rid of the apostrophe. As I sort of got the answer right it wouldn't let me report the answer for being incorrect. As demonstrated above the apostrophe is needed...
There is a technical problem in Duolingo about trailing apostrophes.
So, how do you say in Czech:
1) can you see her parents' house?
2) can you see his parents' house?
3) can you see their parents' house?
jejích, jeho, jejich