Janet Jackson's mother encouraged her to get pregnant.

Janet Jackson

Janet Jackson

The 49-year-old singer - who will turn 50 on May 16 - is reportedly expecting her first child with husband Wissam Al Mana, and she was advised to take steps to start her family before it was too late by 86-year-old matriarch Katherine Jackson, who raised the subject with her famous daughter last autumn.

A source told the New York Post newspaper's Page Six column: "[Katherine Jackson] said to Janet, 'You cannot afford to wait too much longer. I was already a grandma at your age.' "

And Katherine is said to be "thrilled" the 'Together Again' hitmaker took her advice and will be making her a grandmother for the 28th time.

The source added: "It would mean that all of her children have given her grandchildren.

"She hopes that she can be in the room when Janet gives birth."

Despite Janet's advancing years, news of her pregnancy wasn't too much of a surprise to fans as she announced in April she was postponing her 'Unbreakable' world tour indefinitely as she and her 41-year-old spouse were "planning" their family.

She said in a video message to fans: "Hey you guys, on August 31 I launched the 'Unbreakable world tour.

"First I want to thank all the fans for coming out and seeing the show, you guys made it so enjoyable each and every night.

"We are in the second leg of the tour and there's been a sudden change and I thought it was important you be the first to know.

"My husband and I are planning a family so I'm going to have to delay the tour.

"Please, if you can, try and understand it's important that I do this now, I have to rest up, doctors orders, but i have not forgotten about you, I will continue the tour as soon as I possibly can (sic)."

She previously postponed 29 US dates on the tour after being advised to have surgery and rescheduled them for July and August.

In announcing the postponement of the US tour, Janet appealed to her fans for prayers.

She said on her website: "Hey you guys...Happy Holidays to each and every one of you! I need you to know, I learned today, from my doctors that I must have surgery soon.

"It breaks my heart to tell you that I am forced to postpone the 'Unbreakable Tour' until the spring.

"Please pray for me, my family and our entire company during this difficult time...There will be no further comment."