The klever Kardashian! Kourtney dresses baby Reign in Penelope's hand-me-down sneakers as they join Khloe at LAX 

Her sister Kim Kardashian splurges thousands on designer outfits for daughter North.

But Kourtney Kardashian proved herself to be the canny one in the family on Sunday, as she dressed baby son Reign in his big sister Penelope's hand-me-downs.

The nine-month-old wore a pair of three-year-old Penelope's old animal-print sneakers as he joined his mother and auntie Khloe for a flight out of LAX.

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Recycling: Kourtney Kardashian dressed baby son Reign in his big sister Penelope's hand-me-down sneakers as they jet out of LAX on Sunday 

Recycling: Kourtney Kardashian dressed baby son Reign in his big sister Penelope's hand-me-down sneakers as they jet out of LAX on Sunday 

Shoes galore: The leopard-print baby footwear, designed for girls, can be seen in an Instagram snap of Penelope's shoe closet, posted in January. They retail for just under $100

Shoes galore: The leopard-print baby footwear, designed for girls, can be seen in an Instagram snap of Penelope's shoe closet, posted in January. They retail for just under $100

Of course, this being the Kardashians, they were some fancy cast-offs – a leopard print pair by Polo Ralph Lauren.

The baby footwear, designed for girls, can be seen in an Instagram snap of Penelope's shoe closet, posted in January. They retail for under $100.

But while she's thrifty, Kourtney, 36, certainly didn't lower her stylish standards. Both she and Reign wore rock-inspired outfits. 

Rocker chick: The raven-haired beauty, 36, sported a head-to-toe black look, including a leather jacket over a graphic band T-shirt, leggings, and peep-toe ankle boots

Rocker chick: The raven-haired beauty, 36, sported a head-to-toe black look, including a leather jacket over a graphic band T-shirt, leggings, and peep-toe ankle boots

Styling at a young age: Nine-month-old Reign sported a denim jacket over a black top and black trousers, along with his flashy footwear

Styling at a young age: Nine-month-old Reign sported a denim jacket over a black top and black trousers, along with his flashy footwear

Look rocker chic in Saint Laurent like Kourtney

Kourtney Kardashian is definitely the most lowkey of the Kardashian Klan, so it's no wonder she's mastered the effortless cool look. Kourtney chose to layer on a classic Saint Laurent jacket over a graphic tee. The mother of two masterfully pieces together luxe leather separates for a simple, but ultra glamorous ensemble.

Saint Laurent is a favorite of many celebrities, including the rest of the Kardashian girls, Angelina Jolie and Kate moss. The French label embodies the quintessential Parisian cool and carries perfect basics for any look.

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The raven-haired beauty sported a head-to-toe black look, including a leather jacket over a graphic band T-shirt, leggings, and peep-toe ankle boots.

She finished off the look with a chic purse and oversized sunglasses.

Reign sported a denim jacket over a black top and black trousers, along with his flashy footwear.

Not present were his older siblings, Penelope and five-year-old Mason, who were perhaps in the care of their father, Scott Disick. Scott, 32, and Kourtney recently split. 

Mother son outing: Not present were Reign's older siblings, three-year-old Penelope and five-year-old Mason, who were perhaps in the care of their father, Scott Disick

Mother son outing: Not present were Reign's older siblings, three-year-old Penelope and five-year-old Mason, who were perhaps in the care of their father, Scott Disick

Independent woman: Kourtney and her longtime partner Scott Disick recently split and she has been adjusting to the single life 

Independent woman: Kourtney and her longtime partner Scott Disick recently split and she has been adjusting to the single life 

They were also joined on the excursion by Khloe, 30, who went for a more sophisticated head-to-toe black look. 

She sported a trench coat and exotic knee high boots, adding some contrast with a stately Givenchy beige purse.

Meanwhile, Kourtney and Khloe's sister Kim, 34, is known to splurge on designer outfits for her two-year-old little girl, North.

According to Us Weekly, North's closet is stocked with Hermes, Alexander Wang, Stella McCartney, Celine, Lanvin, and Balmain.

Auntie: They were also joined on the excursion by Khloe, 30, who went for a more sophisticated head-to-toe black look
Auntie: They were also joined on the excursion by Khloe, 30, who went for a more sophisticated head-to-toe black look

Auntie: They were also joined on the excursion by Khloe, 30, who went for a more sophisticated head-to-toe black look

North's least expensive articles of clothing were reportedly a $200 Roberto Cavalli leopard print dress and $350 Oscar de la Renta gown. 

A source for Perez Hilton claimed that the little girl even has her own stylist.  

The insider said: 'The tailor, who is also paid to act as North's stylist, works with Kanye and Kim's styling team to create the toddler's looks. 

'Some are collaborations or commissions to designers themselves, and others created in-house.' 

The source also claimed that meetings are held to determine what North should wear, and that many of her outfits are designed to coordinate with her mother.

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