And not their partners?
If two parents are separated and one of them becomes unwell (not just a cold but actually very poorly and unable to look after the DC kind of unwell), it should be automatically the other parents responsibility to look after the children and not the unwell parents partner or spouse?
They can if they want to obviously but the initial assumption should be that the other parent will parent their children even though its not "their time" when the other is not able to? Providing both are involved parents.
Aibu to think this is the case and that it's quite entitled to make assumptions that your co parents partner/spouse will look after your DC when the other parent is unwell intstead of you?