Victor Marke, aged 59, of Mavis Avenue, Ravenshead, was found guilty of 14 counts of sexual activity with a child in relation to one victim, and four counts of indecent assault against the other.
Zara Marke, 35, of Taurus Close, Mansfield, was found guilty of 14 counts of sexual activity with a child.
Zara – also known as Zara Phythian – appeared in hit Marvel movie Doctor Strange, alongside Benedict Cumberbatch, and set up Personal Best Academy, teaching martial arts from its centre on The Broadway, almost opposite Mansfield Police Station.
Sentencing was adjourned until next week.
Detective Constable Paula Wilson, of Nottinghamshire Police, said: “I am delighted this case has now concluded and relieved for the victims that justice has been served and the jury has come to the decision it has.
“This was a long and complex investigation made all the more challenging by the sheer volume of digital data we had to retrieve and examine, and the number of witnesses that were spoken to.
“Like all perpetrators of sexual abuse, the Markes were eventually undone by the determination of the victims who showed bravery and strength in coming forward and seeing this case through to the end.”
Detective Inspector Parminder Dhillon, senior investigating officer, said: “I want to thank the two victims who have showed great courage in coming forward and talking about their ordeal.
“Although no punishment handed down by a court can undo the lifelong damage caused to the them, I do hope they take some degree of comfort from the knowledge justice has now been done.
“I hope this case serves as a reminder to others – that we treat all allegations of sexual abuse with the utmost seriousness and that, even in cases where offences occurred many years ago, we will thoroughly investigate and we will do everything in our power to bring perpetrators to justice.”