I find it hard to sympathize with one group of friends whom want more, and another group whom cant have it at all.....
Why do you need to sympathise with 'either side,' I know if these particular people were my friends, given that I have experienced the joy and love of raising a child myself I would be understanding & supportive to all of their situations. Just because one group can't have any children, doesnt mean the other group should feel bad for wanting to have more.