Ross Mckenzie, baby girl born auckland 1962-64

Looking for my only uncles, only child. She was born in Auckland around 1962-64, i believe she was named Karen Ann Mckenzie on her birth certificate. Her mothers nick name was Peggy. Ross and Peggy were not married and later seperated. My uncle ross has since passed away and my family would love to contact this woman. I believe Peggy was originally from rotorua. I realise i don't have much information but if anyone has anything they think may be of some help tracking either the adopted girl or her mother "peggy" myself and my mother would really appreciate it.