Issue with "What Is Wrong With This Family?"

https://py.checkio.org/mission/wrong-family/

Hi,

While looking some solutions, I noticed they don't actually clear a test case I wrote for myself:

    assert is_family([
      ['Jack', 'Mike'],
      ['Logan',  'Mike'],
      ['Logan', 'Jack'],
    ]) == False, 'Two fathers'

To me, and given the requirements it looks like conditions that should be checked but maybe I am missing something?

Example of problematic solutions (related):

https://py.checkio.org/mission/wrong-family/publications/Sim0000/python-3/first/

https://py.checkio.org/mission/wrong-family/publications/przemyslaw.daniel/python-3/7-liner/