"Potřebujeme jména jejich matek a otců."

Translation: We need the names of their mothers and fathers.

[Laszlo.Sz]

The correct translation would be: We need their mothers' and fathers' names. That is, the apostrophes indicating possession are missing. Unfortunately, there is no option to indicate this error with the feedback button.

[kacenka9]

That translation is accepted as well.

[Laszlo.Sz]

Yes, it is accepted, but it says that there is a typo in it. It says that the correct translation is without the apostrophe. This typo warning occurs all the time with possessive plural nouns. Probably it's a system error.
(Of course, ”We need the names of their mothers and fathers.” is also correct.)