Farrah Abraham honored daughter Sophia's late dad on Monday by visiting his grave. The 25-year-old "Teen Mom OG" star paid tribute to ex-boyfriend Derek Underwood on what would have been his 27th birthday. "Happy Birthday Daddy Derek! We all love you so much thank you for always watching over us," she captioned a photo of flowers and gifts at Underwood's resting place. Abraham was pregnant but not dating Underwood when he died in a car crash in December 2008. She gave birth to Sophia two months later. "He was my first love, my only true love," the star said in her 2012 memoir, My Teenage Dream Ended. "We hadn't spoken in more than two months, but crazily I had still hoped we had a future together." Abraham said in an interview with Bethenny in 2013 that she believes she and Underwood have reconciled after Sophia was born. "We would have definitely probably gotten married and got to experience all of those things in a marriage and let that blossom," she said. "I probably wouldn't be where I am if I had that life." Abraham has since dated Daniel Alvarez and Simon Saran. She denied she and Saran are back together in April after getting close to the real estate agent in Key West, Fla.