I have an only DS (12). I was unable to have another child due to having a brain bleed bought on by pregnancy.
I did struggle initially with the thought of DS being an only and sometimes I still do, but I would say that without a doubt I have coped better as he has got older.
DS seems to have coped and thrived and I don't think it has been an issue for him.
I am an only child as is my mum and I don't think either of us struggled because of it. Of course it's natural to look at big happy families and want that at times but for every one of these families there is a warring family or one where siblings are indifferent.
I do have quite a large family now as DH is one of three and I have some lovely friends also.
As DS has approached his teenage years I feel less the 'odd one out' for having an only child. His friends seem very interested in their own friends at this stage and are forming friendship groups rather than spending lots of time with siblings.
I have made an effort to DS maintain friendships and spend time with friends by being open to sleepovers, giving lifts etc.. This is easier when you only have one child as there is less juggling required.
As time passes I see that really every family is different, all have challenges and differences. Being an only isn't what I wanted for DS but it's where we are and things are just fine. He is a lovely boy, he's growing up fast but still has a kind sunny disposition and I wouldn't change a single thing about him.
They grow up so fast and I try to make the best of every moment that we have together. I think life for me would be much more hectic with several DC, I've been able to work PT, volunteer and have bits of time just DH and I which I'm thankful for.