Presley Gerber has tattooed his sister's name on his arm.

The 18-year-old model visited Bang Bang Tattoos in New York City during Fashion Week in order to get his 16-year-old sibling's name inked on his arm, along with the number 23 in Roman numerals.

Kaia was with her brother when he got the 'Kaia XXIII' tattoo, as was his girlfriend Charlotte D'Alessio, 19.

Presley shared a picture of his new body art on Instagram and simply captioned the picture ''23''.

And model Kaia posted the picture on her account with the caption: '''presleygerber best big bro ever'', along with three broken heart emojis.

Presley even got the seal of approval from his famous parents Rande Gerber and Cindy Crawford, with Randy commenting on Instagram ''RG + JG APPROVED!'', while Cindy simply added: ''Cool.''

Presley did not explain why he chose the number 23, although his birthday is on July 2, while his sister's is on September 3.

Presley and Kaia are currently starring in the Calvin Klein Spring 2018 denim campaign and Kaia has previously spoken about how much she loves working with her brother.

She said: ''I love working with him and every time we book a job together I get excited. At first when we were starting out, we used to shoot a lot together and we would just be there for each other, which is important, especially just starting in such a scary industry - to have someone there that you're comfortable with.''