Kensington Palace refused to confirm or deny William was planning to be at Wembley, and a spokesman would only say the two events will not take place at the same time, reports the Telegraph.
The spokesman said: 'We have not gone into the timing of the the wedding but made it clear that the wedding and the FA cup final will not clash,' she said.
If Aston Villa fan William was to show his face at the final, it would likely be a surprise for the FA, who previously indicating they might have to find a non-royal to present the trophy.
The wedding could lead to a TV coverage clash of the first major royal wedding since 2011 and the biggest football match of the year in Britain.
The date also means Harry and his fiancee will not to marry on either the early May or late May bank holidays as wished for by some working Britons.
And May 19 ensures that the wedding will not overshadow the birth of the Duke and Duchess of Cambridge's third child in April and allow Kate the time to recover.
A royal aide said Harry and Meghan opted for a weekend wedding because they wanted as many members of the public to be involved as possible, whether by watching it on television or attending in person at Windsor.
The Mail understands Harry and Meghan were keen to avoid the possibility of having to declare a bank holiday and wanted the wedding to seem more informal.
'Most couples get married on a Saturday and it wasn't as if they had to worry about another couple already having snagged the date,' said a source.
The Mail revealed the Archbishop of Canterbury will marry Prince Harry and divorcee Meghan, in another sign of changing royal and religious mores.
In a radio interview yesterday Justin Welby declined to say whether he would officiate at the service, saying only that it was 'up to them'.
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But the Mail understands that he has, in fact, already agreed to marry the couple in St George's Chapel at Windsor Castle in May.
The Suits star, 36, will be baptised and confirmed before the ceremony at St George's chapel in the grounds of Windsor Castle.
May 19 is an inauspicious day for one former royal because it was when Anne Boleyn was beheaded on the orders of Henry VIII at the Tower of London in 1536.
Royal weddings usually take place on a weekday. The Duke and Duchess of Cambridge wed on a Friday and the Queen on a Thursday.
Kate's sister Pippa married on May 20 this year.
Commenting on the fixture clash, an FA spokesman said: 'Saturday May 19 promises to be a wonderful day with such a special royal occasion being followed by English football's showpiece event, the Emirates FA Cup Final.
'With millions coming together to watch both events at home and around the world, it will be a day to celebrate.'
Harry and Meghan's engagement was announced by the Prince of Wales on November 27, with Harry saying he was 'thrilled' to be marrying the Suits star – admitting he knew she was 'the one' from 'the first day we met'.
In the Sunken Garden at Kensington Palace last month, Meghan showed the world her engagement ring designed by Harry himself - containing two diamonds from Princess Diana's own personal collection set in a gold band.
The prince proposed in early November after getting permission from the Queen and Meghan's parents. They had been engaged for almost a month before announcing the news.
Royal protocol dictated that fifth in line to the throne Harry had to ask his grandmother the Queen for permission to marry and she agreed in the month where she celebrated her own 70th wedding anniversary.
Harry revealed a year ago he had fallen for the actress after a four to six month secret relationship.
