L.H.
I would discuss this with your HR contact. These kinds of negative comments can be considered hostile and/or discriminatory - especially if they are directed toward you. Your HR contact should be able to help judge the situation and help you find a way to handle the situation with your coworkers.
Coworkers that don't have kids often think policies that allow for maternity leave and time off for dealing with family illnesses are unfair. They think of them as benefits that they don't get to enjoy. They often end up taking it out on their coworkers even though you have nothing to do with creating the policies.