The former TOWIE star told ITV's Loose Women that his uncle Eddie is battling cancer and he's chosen to take part in a charity walk to raise money, a walk that takes place the same week Michelle flies abroad to start work on BBC drama Our Girl.
He said: "My uncle is currently really strongly fighting cancer and we are doing a 14-mile walk for Royal Marsden, the hospital he is with, to raise some money. That's the week Michelle actually goes to South Africa. So I can't go with her but I will be going out to join her."
Uncle Eddie was in the audience, alongside former TOWIE star Elliott Wright, and said he was "feeling great, thanks" when asked by the panel.
"Family is everything to me," added Mark.
Michelle is getting ready to fly to South Africa to begin work on the new series of BBC drama Our Girl. She plays army medic Corporal Georgie Lane, who gets caught in a dangerous mission in a war-torn area of Africa.
Mark told the panel he would be visiting Michelle on set abroad but they'd also stay in touch via FaceTime.