Kate Middleton is said to be getting broody nowadays especially given the fact that her youngest child, Prince Louis, will soon start school in September. A royal author said that she could go for baby number four with Prince William.

The Duke and Duchess of Cambridge may have their hands full right now with three children, but she reportedly feels sad knowing that Prince George, Princess Charlotte, and Prince Louis will all enter school and they will no longer be around to fill the house with raucous joy during the day.

A source told Closer magazine that Kate Middleton has "always been broody and would love another baby." However, it would take Prince William "some convincing as she's had three tough pregnancies and he feels they're 'done.'" The 40-year-old "knows she'd have to do it soon if they were to add to their family and is torn over what to do."

The insider added, "Even though Louis can sometimes be a bit of a handful, Kate feels he's growing up too quickly as he'll also start school in September, and she wonders how empty things will feel when there are no little ones running around during the day."

Royal biographer Katie Nicholl chimed in and said that it would not be a surprise if Kate Middleton "could go for number four" with Prince William. She noted that the duchess "has made no secret of the fact she's broody."

The author of "Kate: The Future Queen" explained, "She's always been extremely close to her sister – they see each other and speak all the time – and the Cambridge children are very close to Pippa and James' children. There's speculation that Pippa is pregnant, so I'm sure Kate will be a support to her through that. And it could make her more broody!"

Kate Middleton admitted earlier this year that Prince William always worries about her meeting under-one-year-olds because when they go home she would say, "Let's have another one." The source said if the duchess could only have her way, she "would love a little sister for Charlotte, like she has in her sister Pippa."

Prince William, Kate Middleton and their children
The Duke and Duchess of Cambridge, Prince William and Kate Middleton, with their children Princes Louis and George and Princess Charlotte. Comic Relief/BBC Children in Need/Comic Relief via Getty Images Comic Relief/BBC Children in Need/Comic Relief via Getty Images