The Texas-born Smith, 40, died of an accidental overdose of prescription drugs Feb. 8, 2007. She left behind her infant daughter Dannielynn, whose father is Birkhead, one of Smith's former lovers.
After a high-profile custody battle following Smith's death, Birkhead gained custody of Dannielynn.
On his Web site (http://www.larrybirkhead.net), the popular tabloid target wrote: "I love you and hope you are proud of our beautiful baby girl. Please watch over us and guide us on our journey through life. We miss you. Love, Larry and Dannielynn."
Smith was a model and reality TV personality who made headlines when she married billionaire J. Howard Marshall, a man 63 years her senior, and then battled with his family for years for control of his fortune after he died.