Which preposition to use with undutiful

of Occurrences 1%

A fico for you, madam," said the most undutiful of great-great-grandsons.

towards Occurrences 1%

Lucy, on her part, angelic creature, professed that she could not dream of being undutiful towards kind old Pa; and that, unless desperate measures were resorted to, quamprimum, in the twinkling of a bed-post she would be under the disagreeable necessity to bundle and go with the disabled man of war to the temple of Hymen.

Which preposition to use with  undutiful