Yago Reidijk, a Dutch convert, was 23 when he wed the 15-year-old who travelled from Bethnal Green, east London, to IS-controlled territory with two other schoolgirls in 2015.
Speaking to the BBC from jail in Syria, he said before the ceremony Begum gave him a list of “weird” questions and requests including whether she would be able to visit friends.
He said: “I just wanted a partner who I could find some rest with and who could take care of me.
“I asked if she knew how to cook and she said yes.
“Our meeting was 10 minutes max. We decided we wanted to try it. We don’t have such a thing as dating or going out and having a meal together. You get to know each other a bit and then if you click you decide to take this step.”
Begum, who was also interviewed for the documentary, said she had spent her “entire life” with women so “being with a man was a new concept to me”.
The couple were married by an ISIS judge and Reidijk said Begum, who was only 15 when they married, did not “have a lot of life experiences”. He said: “They wasn’t much of a person to get to know.
“Most of her life experiences she has today are the experiences she had in the Islamic State as I got to know her. She was basically an empty paper.
“She had got a little bit of understanding about how the married life worked, so that helped her out a lot.
“Respecting of the husband, trying to please the husband and obedience.”
Asked about whether she was comfortable marrying an ISIS fighter, Begum said: “Before I married him I guess he was. I mean I thought he was doing the right thing. I thought he was fighting for his religion and the state.”
The couple had three children but all the died – one of pneumonia and the others of disease or malnutrition.
Begum’s lawyers told an appeal against her the rescinding of her British citizenship there was “overwhelming” evidence she was groomed and trafficked by ISIS for the purpose of “sexual exploitation and marriage to an adult male.”
Reidijk is now in prison in Syria where he is held by the Kurdish forces who captured him.