ashlee-simpson-engagement.jpgsimpson-sisters-engagement.jpg

Their outfits are somewhere between Game of Thrones and Burning Man, but you can't deny how cute these two are together!

Ashlee Simpson tweeted the photo above last night and wrote, "What an amazing engagement party with all of our loved ones! We gettin' married :)." Ash was joined by her older sister Jessica, who added the other shot and wrote, "Celebrating my best friend and sister @missbananahammock @ashleesimpsonofficial. I love her so much!" Ash's outfit may be totally out there, but we can't stop staring at her big sister's hot bod!

It was also Evan's mom Diana Ross' 70th birthday, and the legendary singer will have a very heavy hand in planning their wedding. "She's involved in all levels of my life. She's one of the most incredible mothers ever," Evan told E! News a few weeks ago. "She's involved in every piece of our wedding [and] engagement party.

The duo got engaged in January 2014 after dating for about 6 months. While it seems like it happened quickly, both Evan and Ash have spoken out about how they knew it was a match. "Honestly, we could go and get married right now, wherever," Evan continued. "We just want to be married. We're in love. This is the most incredible time I could ever think of in my life and I'm young, but the same time, I've lived a different life than most and I can't think of a happier moment."