John McEnroe felt unprepared for the “whole new level of fame” he experienced after marrying Tatum O’Neal. The former tennis champion tied the knot with the Oscar-winning actress in 1986 and they went on to have three children together – Kevin, 36, Sean, 34, and Emily, 31 – before the marriage broke down and they separated in 1992. John has now opened up about the relationship, telling The Big Issue magazine: “I was someone who believed in flying under the radar, but it happened that my ex-wife was very famous at a young age. “I thought it made total sense. I was thinking that this person has …