Normally if twins were born on tbe same day time would, or should be on the birth certs as far as I understand
My husband was told he was a twin born circa 1939, home birth but there is no registration, and he never found any other details but the fact your friends twin was registered he must have gone somewhere, adoption sounds, a possibility, if she has the birth cert it might be easy to find a death, but he could still be alive judging by his birth date
LM
Sorry Liz, crossed reply