Ross and Clare Simons had just been given the go-ahead to start fertility treatment. They celebrated the news on Saturday night with friends at a meal.
Less than 24 hours later, Mr Simons, 34, and his 30-year-old wife died when their bicycle was in collision with a Citroen Picasso car in Hanham, near Bristol.
Police said the car struck another vehicle before colliding with Mr and Mrs Simons's bicycle.
A 38-year-old man handed himself in to police hours later. He remains in police custody having been arrested on suspicion of causing death by dangerous driving. A woman, 35, has also been arrested on suspicion of dangerous driving.
Avon and Somerset Police confirmed the matter has been referred to the Independent Police Complaints Commission because an officer had attempted to stop a Citroen Picasso before the collision.
Family friend Diane Pullin said her daughter and son-in-law had been out for a meal on Saturday night with Mr and Mrs Simons.
"They desperately wanted children and it wasn't happening," she said. "They'd just been given the go-ahead. They were so happy on Saturday night."