Eclipse by Lynne Pemberton

A sparkling saga from the author of Platinum Coast. Lucinda Frazer-West: daughter of Lord Nicholas and Lady Serena, a young actress with a glittering future beckoning. Luna Fergusson: daughter of West Indian businessman Royole, reluctantly accepted by his wife Caron, and developing a high-flying business career. Two successful young women, unaware of the bond that links them. They are twins, the product of a one-in-a-million biological chance, following a liaison between Serena and Royole: twin sisters, one white, one black. Now, twenty-seven years later, events are destined to bring them together, and to unmask the secret of their birth.