@itsabeautifulnight
If the decision was taken away from you how would you feel? Relieved or disappoined?
If the former, perhaps its just guilt about your DC being an only child?
People talk a lot about the negatives of being an only child and there's an implication that parents choosing to do it this way are selfish, but there are some considerable benefits as far as I can see from my friends.
My godson is an only child (now 17) and he's always had a great relationship with his parents, was much more likely to join in with adult conversation from a young age, as interested in the world and read a lot, perhaps partly because he wasn't bickering with a sibling over whose turn it is to lay the table/sit in the front seat, etc. He's quite a quiet guy by nature but is lovely, funny and kind, and has loads of friends.
Lots of other examples too.
I'm TTC no.1 and I'm 39 so s/he is very likely to be an only (if I'm lucky enough to get pregnant at all). However my brother and sister had one in the last 6-12 months, and live close, so if I do have a kid, they will see a lot of their cousins.
Not saying it's not worth having. I have siblings, I love them and it's great we get on, but I don't think my life would automatically have been terrible if they weren't in the picture. Just different.