Keane joined Everton from Premier League rivals Burnley in the summer transfer window.
The England international centre-back was in superb form last season and was a key player in Burnley staving off relegation to the Championship.
Keane started his professional club football career at United, but he failed to make an impact at Old Trafford and left the Red Devils on a permanent basis in 2015.
According to a report in The Sun in June, United and Liverpool were interested in signing Keane in the summer transfer window.
Keane has revealed that the Red Devils were interested in signing him in the summer, and has admitted that it was not easy turning them down, adding that his father would have delighted if he had signed for Jose Mourinho’s side.
“They [United] were in touch with my agent and showed a lot of interest,” Keane told The Times. “They wanted me, but a few things happened and I thought Everton would be the best place for me to come.
“I thought I would get a lot of game time here, more than I possibly would at Manchester United, and that was a massive factor in my decision.”
“My family are all Man United fans so it was not an easy decision,” added Keane. “My dad would have been delighted if I had signed for United. But he is glad I have come to Everton and not Liverpool, put it that way.”