Ashlee Simpson has thrown a lavish party to celebrate her engagement to Diana Ross' son. The pop star accepted a proposal from her boyfriend Evan Ross in January (14), and the couple gathered their friends and family together on Wednesday night (26Mar14) for a bash to mark the special news. Simpson shared the occasion with fans by posting a picture on Twitter.com showing her cuddling up to Ross. The singer is wearing a white feather headdress in the shot, while her fiance dons a large furry coat. She added in a caption, "What an amazing engagement party with all of our loved ones! We gettin' (sic) married." The star's elder sister Jessica was among the guests and she published a picture on Instagram.com showing her hugging her sibling, with the caption, "Celebrating my best friend and sister... I love her so much!" Simpson was previously married to rocker Pete Wentz, the father of her son Bronx.