Twin Girls

[Sally74]

Hi, i am new to this site so bear with me!
My husband is looking for his 2 half twin sisters who were born in South Africa between 1960 - 1970. My husband's father was in the Merchant Navy between these times and met a single young lady over there with whom he had 2 twin baby girls. We do not know the name of the lady, nor the names of the twin girls or even if he was put on their birth certificate!
He went back to go and get the girls a couple of years after they were born to bring them back to England but the mother and girls had moved.
We have no idea on where to go from here. The father's name was Edwin Stone. Unfortunately he passed away last year so there is no way of obtaining any more information.
Hoping someone can help me!
Thanks in advance.