This is me too.
I actually had some counselling for this and it has helped. I do have some guilt still but I worry less now than I did.
Same, I explored this in CBT because it was tied into my environmental guilt and my therapist really reassured me about the whole 'but they are desperate for grandchildren' situation.
As an only child, and an only child that is a 'miracle', I did feel enormous pressure. My husband's brother has had two children so he is off the hook.
My Mum's best friend who lives abroad became a grandma a few years ago and she added me on FB. In between her general posts and shares she would post lots of videos and photos about how great it was to be a grandma and my heart broke for my Mum because I knew she would see the same photos and videos.
However, this friend's family really struggled during the Canadian heatwave this year (that
wasn't put on FB) and I think this friend did express to my Mum her fear for her grandchildren's future. I think as well as being a caring Mum and wanting me to be happy (see previous posts) I think seeing her friend experience such acute worry about her grandchildren brought it into focus for my Mum.