If the reports are true, it will be the second wedding in just weeks that Prince Hazza has attended sans his girlfriend.
But, according to enstarz.com, the move is likely to have been decided on together, with the pair wanting to enjoy their privacy for as long as possible.
A source recently said: "Harry and Cressida have made a point of talking about marriage and what changes they're going to have to make to their life of late. According to friends of Cressida's, the couple have decided to try and keep their semi-normal lifestyle as long as physically possible."
The prince recently joined the Duke and Duchess of Cambridge at the wedding of Lucy Meade and Charlie Budgett at St Mary the Virgin church in Marshfield, Gloucestershire at the end of March (pictured above).
It is thought the brothers will be ushers at the ceremony, to be held on 3 May.
LOVE HAZZA? See why we're all head over heels for Prince Harry in our gallery below:
MORE CRESSIDA! See exactly why Ms Bonas has stolen the prince's heart in our style file gallery below:
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