Both of my mother's parents had several siblings and even though Mum was 30 when I was born I would have expected to have known most of them.
My grandmother was the youngest of 5, the only girl, she was orphaned at a young age and was then brought up in an orphanage. She did not lose touch with her brothers, but my mother and I only ever knew one of them.
In researching my family this is what I found.
Her eldest brother who she lived with for a while married and had children he joined the army when WW1 broke out but was discharged as not being considered suitable to be an efficient soldier. However he never saw his youngest child as he died in the influenza epidemic in 1918.
Her brother Sidney was killed in WW1 and is mentioned on the CWGC site.
Her brother Ernest Roy was also lost during WW1 but I have been unable to confirm this as the only possible a Roy COMPTON born Warminster has no age recorded and no parents names.
My grandfather's side of the family was much larger.
He was one of eight. Four girls and four boys. Two of his brothers were too young to serve in WW1 and both his older brother and he survived the conflict. I never met my grandfather as he died 2 years before I was born.
His older brother died the year I married but I have little recollection of him.
Of his 2 younger brothers the youngest was killed in a road traffic accident before my mother was born and she would not have known him and the other remaining brother was a guest at my wedding being the only remaining member of his generation in that part of the family.
Even in my generation I have not known all of my uncles as one of my mother's brother's died the day before her twelth birthday having been involved in a road traffic accident the previous month.
This only goes to show how much world events and tragic accidents can impact on our own families.