Justin Timberlake and Jessica Biel to tie the knot next month, says his gran

Trust gran to let the cat out the bag.

JTs nan inadvertently gave away the date and location as she revealed the 31-year-old singers grandfather will be too ill to attend.

Trousersnakes gran Sadie Bomar said: My husband, Bill, has had problems with his heart for a while now and is undergoing a major heart surgery soon. Bill also suffers from dementia, making it tough to care for him.

Unfortunately, we wont be able to go to Italy with my daughter (Timberlakes mum) in October.

Biel has been playing it rather coy when it comes to wedding talk (Picture: Xposure)

Until now, Biel has been telling everyone that shes been too busy to arrange her big day.

The 30-year-old Total Recall actress said last month: Its very exciting but its hard to find the time for it. Its a good moment just to enjoy it.

I have no idea of what I want. I am one of those people who are not very detailed orientated.

'I dont feel like Im one of those people who is like, This has to be done this way."

'Im more of a big idea person. I will probably give an idea and let it be created, she said.

It was even reported last month that the pair had tied the knot in a secret ceremony at the ski resort of Jackson Hole in Wyoming, the same place Justin popped the question to her at Christmas.

Biel, 30, and Timberlake, 31, got engaged at Christmas but until recently, had been rather coy about admitting their news.

The couple have been dating for nearly four years. They split last year before getting back together just before Christmas.