Beyond Forgiveness by Caro Fraser
A wealthy elderly man knows that he is dying. Haunted by memories of a woman whom he loved, had a child by, but never married, he goes through a secret wedding ceremony with her, and in his will leaves her and their daughter, Abby, 200,000 each. After his death Abby - a single mother on the dole - finds the marriage certificate and discovers from a lawyer that this, plus the strange wording of the will, entitles her to his whole estate and disinherits his legitimate son and daughter. Abby is hardly money-grubbing, but she's determined to claim what is rightfully hers. But complications ensue, as she meets Simon, her childhood friend ...