Bella Hadid has paid tribute to her older sister Gigi Hadid on her birthday.

Gigi and Bella Hadid (c) Instagram

Gigi and Bella Hadid (c) Instagram

The blonde-haired supermodel celebrated her 22nd birthday on Sunday (23.04.17) and her 20-year-old sibling took to social media to gush about her in a heartfelt post, which saw her describe the catwalk icon has her "best friend" for life and praise her for being "so generous, smar, funny, talented, har working, artistic, loving, respectful and beautiful."

The brunette-haired fashion muse shared a string of images of the duo when they were children, as well as more recent photographs of them from fashion shows, and on evenings out together to her Instagram.

And she captioned the upload: "Happy birthday to my best friend FOR F**king LIFE!!!!!!!! My role model! My person. I feel so lucky every day to call you my sister. I didn't know anyone could be so generous, smart, funny, talented, hard working, artistic, loving, respectful AND beautiful all at the same damn time!!! (sic)."

Bella also credited Gigi for her ability to make her laugh "until I pee" and being able to boost her morale when she is feeling down.

She continued: "You make me laugh until I pee and even when I don't want to smile, you are just about the only person that can make me. Every one that knows you, immediately feels the incredible energy that radiates throughout you. Thank you for always being yourself, nothing more and nothing less. You are my other half & I don't know what I would ever do without you. I love you with all of my heart Squeegee. @gigihadid (sic)."

Gigi's mother Yolanda Hadid, 53, has also gushed about her oldest child in a sweet post on social media, to reveal how "proud" she is of her "sweet Angel".

The 'The Real Housewives of Beverly Hills' star wrote: "Happy birthday my sweet Angel...... I pray that each day Love, Health and Happiness will come your way. I'am so proud of the human being that you are and grateful to experience this journey of life with you everyday through the good and the bad. May all your dreams come true this coming year and let it be filled with joy and laughter #HappyBirthday #MyLove #22 #ILoveYou #AlwaysAndForever (sic)."

Zayn Malki, 24, who is currently dating Gigi, has also shared his well wishes on his photo-sharing site.

Alongside a picture of him kissing the American star, he wrote: "happy birthday to my everything (sic)."