Wiebke Konerding the lead researcher at the Hannover Medical School and the University of Veterinary Medicine Hannover, Germany studied the reaction of male vs female cats to distress calls of unrelated kittens.
Interestingly, the more distressed the kittens were, the more the female cats reacted, even if they had not raised kittens themselves. The researchers found that there was no difference between the response of male or female cats to low arousal calls from kittens. But there was a difference to high arousal calls. Only female cats reacted differently.
The study implies that the ability of adult cats to react differently to emotional cues from kittens is ingrained and not due to experience. The kittens used in the experiment were not related to either the male or female cats.
Further research is needed to determine if adult cats react differently to their own kittens then they do to unrelated kittens.