While Prince Louis is known for his playful personality, his older sister Princess Charlotte is widely regarded as the Prince and Princess of Wales's sensible daughter who takes after her mum Kate – and likes to keep her brothers in check.
Both Louis and Charlotte are Taurus star signs, but the young Princess, who turns nine on Thursday, is a more "typical" Taurean, says astrologer Debbie Frank.
© GettyPrincess Charlotte's personality
Speaking exclusively to HELLO!, Debbie said: "Princess Charlotte is more of a typical Taurus than her younger sibling Prince Louis. She is a quick thinker but generally more biddable than the volatile Louis."
Debbie noted: "Her Moon in Libra likes to fit in and do the right thing. Louis' big personality does bring out her more playful side but she's not above bossing him as his big sister."
Prince George's similarities to Princess Kate
The pair's older brother Prince George, meanwhile, is a Cancer and shares very similar traits to his Capricorn mother Kate; both have a "highly responsible nature".
"Prince George's chart shares a similar frequency to his mother," Debbie said. "He has the Sun in Cancer opposite Moon in Capricorn, and she has Sun in Capricorn opposite Moon in Cancer.
"Both have the Sun and Moon in aspect to the stern taskmaster planet Saturn, indicating a highly responsible nature."
She also noted: "Prince George's astrological signature is very different to Louis' chart and as heir to the throne he may have a hard time keeping his younger brother in line in years to come."
© GettyCharlotte ruling the roost
Much is made of six-year-old Louis' cheeky antics and how his older sister Charlotte rules the roost at home and on public royal outings, both with Louis and their older brother George.
In a previous interview with HELLO!, global parenting expert Jo Frost of Supernanny fame, said: "Charlotte knows the rules. She's the one in the middle. She knows how to keep everyone in good stead.
"There are moments when I've watched George and he's looked over at his sister, and he's probably annoyed with her one minute and then grateful that she's there being able to remind him of things."
© GettyCharlotte's ninth birthday
William and Kate are preparing to celebrate Charlotte's ninth birthday on Thursday. The Prince and Princess are expected to release a new photo of their daughter on the day, much like they did with Prince Louis' birthday last month.
Elsewhere, the Waleses usually celebrate their children's birthday in private, and it's likely Charlotte will be showered with gifts and cake at home. Kate has previously admitted that she stays up until midnight the night before baking.
"I love making the cake," the mother-of-three said on Mary Berry's A Berry Royal Christmas. "It's become a bit of a tradition that I stay up 'til midnight with ridiculous amounts of cake mix and icing and I make far too much. But I love it."
Of course, the Princess, 42, is also undergoing preventative treatment for cancer, so her daughter's birthday celebrations may be more low-key than previous years.
