Tom and Olivia were both 23 when they met at the Reno rodeo. Tom was passing through from the end of ranch hand job in the northeast part of Nevada, on his way to meet a friend for a Mexico motorcycle trip in Mexico. He'd be flying from Reno to Los Angeles to the friend. Olivia was a performer in a revue at Harrah's. She said yes when he asked if she'd be interested in a drive to and around Lake Tahoe the next day. The next morning Tom picked her up in his rental, a 1972 Cadillac Eldorado convertible, top down. They took Mt. Rose Highway to Incline Village, turned right to travel counter-clockwise around the lake.
They had lunch on Tahoe City. When they stopped at Emerald Bay to take a picture, Olivia realized she'd left her camera back, resulting in her buying a Kodak Instamatic in South Lake Tahoe, which she used shortly thereafter to take the selfie including Tom on the sandy beach, lake behind them. The plan to continue around the lake to Mt. Rose Hwy. was changed by a fire in the Spooner Lake area, so they too 50 east to 580 north. A stop for dinner in Carson City led to drinks, dancing and staying overnight at the Pony Express Hotel, where Hunter was conceived. Birth control was Olivia's diaphragm.
They next morning they drove to Reno, had breakfast, then Tom dropped Olivia off at her hotel, returned the Cadillac, caught his flight to Los Angeles. Neither had a phone, thus no numbers to exchange. She missed her period, discovered she was pregnant, moved back home into her parents' house in Orange County, California, had Hunter, went back to school at a community college, then to a nearby state university to get a bachelor's in theatre with an emphasis in dance. Throughout, her parents assisted in raising Hunter. They - Robert and Maxine - had adopted Olivia when she was a year old and they were in their early-forties. When Olivia came home to have Hunter, Robert, an engineer for the county, retired.
We learn most if not all of this when Brian asks Barbara about Tom and Olivia.