Meghan Markle and Prince Harry also invited Kate Middleton and Prince William to their daughter Lillibet's first birthday.
The Duke of Cambridge, Prince William, is celebrating his 40th birthday today without his younger brother, Prince Harry.
William's birthday comes nearly three weeks after Prince Harry returned to Britain with his wife Meghan Markle and their children Archie and Lillibet.
The royal couple extended an olive branch in Cambridge by attending Queen Elizabeth's Platinum Jubilee celebrations and inviting her to their daughter Lillibet's first birthday.
According to the International Business Times, Meghan and Harry returned to the UK hoping to repair strained relations with William and Kate, however, they were turned down.
Meghan Markle is reportedly feeling disheartened after she snubbed him during a trip to the UK.
Now, the Duchess of Sussex has warned her husband Prince Harry against giving William and Kate Middleton an 'olive branch' and any first steps towards a reconciliation with them.
The report, citing an insider, claims: 'Meghan believes she needs to stop taking the first step and offer all these olive branches that are thrown back in her face. '
It further claims, Meghan and Harry can't even wish Prince William on his 40th birthday. "They might send a card and small gift, but it's unlikely. The way the Cambridges were with them on the anniversary was sad, and they're not likely to forget it in a hurry."