Kim Kardashian West has thanked her step-father Bruce Jenner for teaching her "so much about life".

She wrote: "Happy Birthday Bruce! You are officially a senior citizen lol! Thank you for teaching me so much about life. I love you so much! Xoxo (sic)"

Kim's sister Kourtney Kardashian, 35, also took to the social networking site to praise the former track and field star – who split from their mother Kris Jenner last year – for being an "inspiration" to her.

In a caption attached to a throwback picture of the ex-sportsman in the USA kit with one of his decathlon medals, she wrote: "Happy birthday Bruce! You have been such an inspiration always. I love you! (sic)"

Bruce's daughter Kendall Jenner, 18, followed suit, posting a picture of her father holding a tennis racquet and adding the caption: "happy birthday to my dad, my everything! (sic)"

But there was no sign of a message from Kris, 58, nor their daughter Kylie, 17, or Kim and Kourtney's sister Khloe, 30, or brother Rob, 27.

What's more, Bruce's sons Brandon, 33, and Brody, 31, from his marriage to Linda Thompson also remained quiet on the social networking site.

Bruce was spotted out and about in Malibu on Tuesday wearing striking red nail polish and holding onto a cigarette.

Kris and Bruce tied the knot in 1991 but the brunette filed for divorce from him last month.