The '99 Problems' rapper will be the one to present the wedding ring when his friend marries the reality star at Forte di Belvedere in Florence, Italy, on Saturday (24.05.14).
A family member confirmed to MailOnline.com that Jay and his wife, Beyonce Knowles will be attending the wedding, saying: ''Beyonce had to think about it at the last minute, she didn't really want to go, but I think Jay Z's the best man, so he's kind of making her go.''
The superstar couple's arrival is eagerly awaited in Paris, where the wedding festivities will start on Friday (23.05.14), before guests are flown to Italy, for the ceremony the next day.
'Keeping Up with the Kardashians' star Kim - who is set to be married for the third time - is said to be worried rain will spoil her big day.
She was noticeably upset when she enjoyed dinner with her family at the Hotel Costes on Wednesday (21.05.14) before visiting the Eiffel Tower and a nearby carousel during a downpour, where she declared: ''I hope the rain doesn't ruin my wedding.''
The onlooker added: ''She made it clear that this bad weather is really getting to her. She's clearly spending millions getting married in Europe, and if it all turns into a wash-out she will be really unhappy.''
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