If you look in the birth register for the quarter in which your Aunts birth was registered (this may be different to when she was born, eg if she was born in March 1960 her birth may not have been registered until April so you would have to look in the quarters ending both March and June 1960) you could see if there is another child with the same surname registered at the same place. If there is you may have to order the birth certificate to find out if it is a twin of your Aunt. If you want to post your Aunts birth name, date of birth and where she was born I could look it up for you, but I understand if you don't want to.