Meghan’s mum Doria Ragland is also said to be moving into the mansion to help the couple raise the new royal tot.
"Doria will be staying with them for quite long periods and they need a larger place,” a source told the Sunday Mirror.
"Frogmore Cottage isn’t massive but it’s certainly big enough for Doria to have a separate area there.”
The Queen gifted the Duke and Duchess of Sussex Frogmore Cottage, which is currently undergoing major renovations.
Once completed the property will feature, ten bedrooms including a nursery for the baby and the couple are expected to move in next year.
"With a baby on the way, there wasn’t the option of the Duke and Duchess staying at the palace as Nottingham Cottage is tiny and none of the bigger apartments are available,” the source added.
However there have been reports that the move could be due to a rift between Harry and his brother Prince William.
“The initial plan was for Harry and Meghan to move out of their cottage in the grounds of Kensington Palace and into one of the main apartments,” a source told The Sun.
"But there has been a bit of tension between the brothers. Now Harry and Meghan don’t want to live next to William and Kate and want to strike out on their own."