Request #170

I am looking for a book title I think was published in the 1970s. The plot: the storyline starts with the heroine in her late twenties living with her aunt (or other women relative) in NYC (?). The heroine had had a baby in her late teens (she had run away and was hooked on drugs). Her rich father had found her just after she gave birth and gave the baby to the heroine’s sister and brother-in-law to raise without the heroine knowing this. She has wondering what happed to the baby. The sister, brother-in-law, “niece”, and their younger son come to stay with the aunt and the heroine due to financial troubles. The “niece” is surly and difficult to get along with. The heroine is friends with the sister’s ex-boyfriend who worked for her father. The brother-in-law is murdered. The heroine figures out her “niece” is her child but decides to not tell the niece. The ex-boyfriend admits loving the heroine at the end of the book. I remember the cover had pink in it with a drawing of the heroine and the ex-boyfriend on it. Any help is appreciate