Khloé Kardashian celebrates 'forever bestie' Kylie Jenner's birthday

Khloé Kardashian has marked her sister Kylie Jenner's 29th birthday with a sweet message.

Taking to Instagram on Monday, the reality TV star posted a slideshow of recent snaps and throwback photos featuring herself and her young half-sibling.

In the accompanying caption, Khloé gushed over her special relationship with the beauty entrepreneur.

"Kylie, I swear in another lifetime I was your mother. I don't care how old you are, you will forever be my baby," she began. "I know I've loved you long before this life and I'll love you long after it. My sister by blood, my best friend by choice, and one of the greatest loves of my life. I know in every lifetime, every reality, every realm, we will always find one another."

The Good American co-founder went on to reflect on how "incredibly proud" she is of Kylie.

"The mother, friend, sister, daughter, businesswoman you are inspires me endlessly. You light up spaces you aren't even in by the mention of your name. You're hysterical, gentle, loving, lighthearted, patient and so much fun and yes, obviously the most gorgeous but your heart will forever be the most beautiful thing about you," The Kardashians personality continued.

To conclude, Khloé insisted she would never take their bond for granted.

"What a blessing that I get to do life with you the way that we do. My forever baby. My forever bestie. My forever soulmate. My forever. I love you beyond words," she added.

In addition, Kim Kardashian offered up her own post in honour of Kylie's special day.

"Happy Birthday my princess kitty baby sis @kyliejenner. I lovvvveeeeee youuuuuuuuu (sic)," she declared.

Over the weekend, Kylie uploaded several photos from a pink-themed "princess kitty" party, with guests including her sister Kendall Jenner and longtime friend Hailey Bieber.