Supermodel Heidi Klum is back on the market. The 40-year-old stunner split from her bodyguard boyfriend, Martin Kirsten, a few weeks ago after an 18-month relationship, RadarOnline.com is reporting. A pal close to the pair confirmed the news to Peoplesaying, â€œMartin was there for her during a challenging time in her life and it was something she will always be grateful for.â€ PHOTOS: Heidi Klumâ€™s Bel Air Home Klum and ex-hubby Seal divorced in 2012 after seven years of marriage and she started dating Kirsten, 41, shortly after. â€œLife is about timing. He was incredibly supportive and they were there for each other, but theyâ€™re moving on now,â€ the source added. â€œThey still have a great friendship.â€ PHOTOS: Theyâ€™re Gorgeous, Theyâ€™re Moms & Theyâ€™re Models! However, Kristen will no longer be employed with Klum as her bodyguard given the nature of their once romantic relationship. Radar reached out to Klumâ€™s rep for comment but got no response at the time of publication.