First Lady-elect Jill revealed she wasn’t put off by their nine-year age gap when they first met in 1975 in her 2019 memoir.
But the newly qualified English teacher said she made sure his sons Beau and Hunter wouldn’t lose a second mother figure.
Their mother Neila was taking the children Christmas shopping in 1972 when their vehicle was hit by a truck.
Both Neila and her and Biden’s daughter Naomi were killed in the horrific crash, but Beau and Hunter survived, despite being seriously injured.
A heartbroken Joe, 77, was left raising their sons alone before he went on to find love with his current wife Jill three years later.
In her memoir, Where the Light Enters, Jill explains that she was also concerned about losing her career and her own identity.
She wrote: “I knew that no matter how much I tried, there would be so much I could not control.
“If I gave Joe my whole heart, he had the power to break it.
“I was launching my career and planning for graduate school – and then I had staff calling to schedule dates with my boyfriend around his insane Senate schedule.”
She went on: “I was being pulled in so many directions.”
But when it came to the fifth proposal, things were different.
Joe went to Jill’s flat on his way to the airport in 1977 and said: “Look, I’ve been as patient as I know how to be but this has got my Irish up. Either you decide to marry me or that’s it, I’m out. I’m not asking again.”
He added: “I’m too much in love with you to just be friends.”
Biden then left, flying to South Africa for political duties, and he finally got the “yes” he wanted later that night.
They married at the United Nations chapel in 1977, taking Joe’s sons Beau and Hunter on their honeymoon.
In his autobiography, Joe said: “She gave me back my life. She made me start to think my family might be whole again.”
They welcomed a daughter together, Ashley, in 1981.