FA Cup finalists Wigan and Manchester City have been given new dates for their Premier League games rearranged because of the Wembley showpiece.
This season's FA Cup final will take place on Saturday, 11 May - 24 hours before Wigan were due to play Arsenal.
The Latics will now travel to the Emirates Stadium on Tuesday, 14 May - the same night City travel to Reading for their rescheduled fixture.
City's game against West Brom, which was due to take place last weekend, will now be played on 7 May.
City's FA Cup semi-final opponents Chelsea will entertain Swansea on Sunday, 28 April because of their Europa League semi-final with Basel the previous Thursday.
Lee Johnson, who played under his father at Bristol City and with the Glovers, became the Football League's youngest manager at just 31 when charged with the task of guiding Latics to League One safety last month.
It is only the second such showdown in English football history - Bill Dodgin led Bristol Rovers against son Bill Jnr's Fulham on the first of five occasions in the 1969/70 season.
But with Yeovil chasing automatic promotion and Oldham having edged away from the bottom three thanks to a battling 1-0 win over Bury on Saturday, pleasantries will be saved for a family meal at Lee's new house in Cheshire on Wednesday.
"We are both fighting for our respective towns, directors, supporters and players so there is a lot resting on both our shoulders," said the Yeovil boss.
"There cannot be any favours, too much rests on each of our clubs getting the three points. The ideal scenario would be that eventually we get promoted and they stay in the division."
The 57-year-old former Northampton and Peterborough boss admits his son's first managerial role comes as no surprise.
"He was always destined for management because he has grown up in that environment since he was really young," he explained.
"I would be picking my team on a Friday night and, as a nine or 10-year-old, he had his opinion. He'd come to all the games and chuck his opinion in.
"I was a competitive Dad and it will probably keep him in good stead for this job where everyone is going to be competitive. I am sure all that has helped over the years and hopefully he has grown up humble as well as competitive."