The publication says that Kate and husband Prince William are thrilled with the news.
‘They were surprised but also thrilled that Kate was pregnant again. They both feel so grateful their dream is coming true,’ the publication's insider alleges.
WATCH: Rare footage emerges of the Queen chasing a young Prince William
‘Kate recently found out that she’s having twins – two girls!’
The US publication’s source says that Kate was ‘absolutely speechless’ and ‘didn’t fully believe it until she heard it for herself.’
According to the source, husband Prince William is equally delighted and ‘melted’ when he heard the happy news.
‘Charlotte is the light of his life, so to have two more girls to spoil him is going to be absolute heaven for him.’
Meanwhile the couple are said to be busy ‘figuring out all the logistics of how they will easily transition from a family of five to a family of seven.’
‘Right now the plan is to move Charlotte down the hall into a “big girl” bedroom so the babies’ nursery will be closer to Kate.’
And William has even told friends that the couple will name one of the girls Diana as a ‘touching tribute to his late mum.’
Kate Middleton earlier this week fuelled rumours that she and Prince William might have some news while dancing with a baby at the RHS Garden Wisley.
Following her entrance to the event via tractor with British TV personality Mary Berry, the Duchess of Cambridge got in touch with her maternal side as she played with children at the Back to Nature garden launch.
Wearing a floral dress by Emilia Wickstead, the mother-of-three was seen laughing and dancing with a small baby.
A local Australian publication reported that she told the child's mother that her son Prince Louis loves to "smell flowers in the garden."
Kate also spoke to families who were invited from the Evelina London Children's hospital - one of the royal's patronages - as she planted a blue cedar tree at the RHS Garden Wisley's new space for families.
The Palace has yet to respond to OK! USA's claims.
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