AceShowbiz -

Will Prince George and Princess Charlotte welcome a new sibling soon? Kate Middleton is said to be pregnant with her third child, but she hasn't told anyone besides Prince William and some of their closest friends.

According to Life & Style, Kate and William really want to tell George and Charlotte about her pregnancy. "William and Kate can't wait to tell Charlotte and George that they're going to have a brother or sister," an insider tells the publication. "They think Charlotte is too young to fully understand, but at nearly four years-old, Prince George will be excited about the news."

However, the Duchess of Cambridge is worried that Charlotte won't be happy with the news. "She is worried that Charlotte will be jealous at first," the insider claims. "Charlotte loves being the center of attention and is strong-minded." George, meanwhile, is said to be "more laid-back" and will be an excellent brother for his siblings.

Although Kate and William haven't announced her pregnancy, the couple has reportedly started choosing names for their unborn baby. "They like the names Edward or James for a boy, and Isabella or Olivia for a girl," the insider shares.

Kate's sister, Pippa Middleton, is also believed to be planning to have children soon. "Pippa and Kate are extremely close and have discussed how it would be fun to have children at the same time," the insider says. "They've been looking at baby clothes online together!"

Last month, it was reported that Kate was pregnant with a baby girl. "Kate is about 15 weeks along," a source revealed, before adding that she was "expecting a baby girl in November." The source further claimed that she and William were planning to ask Prince Harry and his girlfriend Meghan Markle to be godparents.