My Blood Runs Cold (1965)

Wealthy, reckless Californian Julie Merriday, accompanied by her boyfriend Harry Lindsay, an attorney, narrowly avoids crashing into a motorcycle driven by young Ben Gunther. Ben temporarily abandons his damaged cycle and accepts a ride from Julie but insists upon calling her Barbara. Later, at the Merriday beach house, Julie's Aunt Sarah tells Julie that her great great grandmother was named Barbara, and furthermore, that ancestress had an illegitimate child fathered by one Benjamin Gunther.