Watch: Trump-Russia investigative reporter reveals why entire Trump family will be snared by Russian investigation

On Friday, CNN's Don Lemon had Seth Hettena, author of Trump/Russia: A Definitive History, to discuss Hettena's extensive reporting on the subject of the Trump family's business dealings in Russia, including the Trump Tower Moscow deal.

"This was sort of your 'I told you so' moment," Lemon said by way of introduction.

"You know, you said it at the outset, right. This is about money. And Trump has been chasing Russian money forever, since 1987 he's been going to the Soviet Union... and it just has never stopped," Hettena said.

Lemon asked Hettena about reports that Mueller is intensely focusing on the roles of Don Jr. and Ivanka in the Moscow project.

"How deeply are the children involved in all of this?" Lemon asked.

"Well, they're involved. You know, this hasn't gotten much discussion, but Ivanka picked the architect for the Trump World Tower. In the letter of intent, it said that there is going to be a spa by Ivanka in the building. Don Jr. was involved. He was a kind of a go-between between the family and Russia. So I think the kids are probably even more involved than Trump himself," Hettena said.

"Don Jr. has testified to the house," Hettena said. "Devin Nunes hasn't released any of those transcripts but those things are going to come out, and it's going to be interesting to see what's in those things."

How did the Trumps end up in this mess with Russia? Hettena said it was because people in other countries didn't want to do business with the Trumps.

"Trump is not going to be welcomed in London. Canada is not going to be embracing him. But Russia, where there's bigger than life characters, Trump is like a natural fit. And I think he goes where he feels accepted and loved, and I think he's always felt accepted in Russia," he said. "Trump comes from this New York kind of rough and tumble world, and I think that's the way business is done in Moscow. And I think, you know, he likes to live large, and that's what Russians do... Trump doesn't like to play by the rules, he doesn't like to pay taxes. He doesn't like to do business the way it's -- you know, under rules. In Russia, the rules can be bent if you know the right people, if you have the right connections. Yeah, I think that's a natural fit for Trump."

Watch below.