Could anyone help me work this out regards my National Insurance number - UK?

I have recently relocated to the UK as I have lived abroad most of my adult life. I have been trying to get my National Insurance Number it appeared that I did not have one. Finally I was sent to a head office to try and find it, quite prepared to apply for a new one.

When I got there it appeared that I have been ‘deleted’. This is strange? My brothers were there so were my parents. My one brother is deceased as are my parents.

Why would I have been deleted?

I ask because, when I questioned the staff regards this they seemed very puzzled. Until I mentioned that when my mother was suffering dementia like symptoms she mentioned that I had a twin that they had given up for adoption. This was news to me, so I put it down to ramblings. I did mention this to the staff and they confirmed that in such a case it would be a matter of human error that I was deleted by mistake. As in the wrong twin was deleted.

I am not sure what to think, perhaps I do have a twin? I am told we all have a number the moment we are born (in the UK?). Or is this something that can simply happen?

My ‘case’ file has been sent for further investigation. I am not sure what to think?