You don't specify why you can't do both. I've rigged up a passable bike trailer that could have carried a person, and I'm sure I could do it again. There's a lot of criteria missing here. I'd say on the face of the discussion, I'm bringing everyone with me. If the question is more like "one person is injured and can not be moved", then that changes things. Only a selfish parent would ask you to stay if there were kids involved.

I would say this... if one parent is down and can't be moved due to injury or they are "stuck", then I'm leaving them with enough resources to survive for a while before I just walk away with the kids. And I would fully intend to come back or at the very least send help with as much information about location as possible. If the kids are old enough to fend for themselves (16-18?) and they have a good Bug Out location, I send them ahead by themselves.

Also, since the criteria also imply that there is devestating weather/fallout or other natural or unnatural event that means staying behind presumes death for that person, it would be heartbreaking, but the best option is to say your goodbyes and go if nothing can be done.

But I'm with Sue on this. If you have things so badly planned that you are stuck in this situation.... Granted, I suppose someone could get hurt while making an exodus from a danger zone, despite their planning...

Kids are the deal breaker.