Martin is also retiring as United’s chief scout later this year, leading some to suggest a brotherly pact may have been agreed.
Martin told his brother he reckoned the announcement came out of sibling rivalry.
He joked: “I told him I knew what he was up to, trying to steal my thunder ahead of my retirement.
“I told him that I had all the press and television lined up for me making my own announcement but now he’s gone and spoiled it.
“He burst out laughing, of course. We didn’t make any pact and we didn’t discuss it at all.
“It just seems that the time was right for both of us. For God’s sakes, we’re both old enough. I hope we manage to see more of each other and the families spend more time together because he is a great family man and he looks after his family extremely well.”
He added: “He absolutely dotes on his grandchildren and I think having more time with them is something that he will appreciate.”