Translation:Who showed František's and Kateřina's friends where we live?
To me the phrase "František's and Kateřina's friends" sounds unnatural and I would never say it -- I'd only say "František and Kateřina's friends". It's ambiguous, but much more natural to my ears than the suggested translation. I reported it but want to know if anyone here agrees with me.
I feel a difference in meaning.
"Bob's and Mary's friends" = Bob's friends and Mary's friends". His friends and her friends are two different groups. There may be some overlap between the groups, or there may not.
In contrast, "Bob and Mary's friends" points to one group of friends that the two have in common.