The siblings teamed up to promote Graham's Swimsuits for All campaign, showing photos from their childhoods as well as today to show off how tight they've been through the years.
"Despite our six-year age difference and busy lifestyles, my little sister and I have always been strong presences in each other's lives," Graham said in a statement. "We've shared countless memories together and going through our childhood photos was a trip down memory lane. Abigail has always been my rock, and I was honored to have her by my side during this photoshoot. Plus, she's a new mom and has never looked hotter in a swimsuit!"
Abigail added, "I love to support Ashley in everything she does, especially when it comes to promoting her message of beauty beyond size. As children, Ashley and I created a very tight bond that we have been able to carry over to adulthood. Every summer, we would go on road trips together to different states. I'll never forget Ashley getting stung by jellyfish in Florida. It was hilarious! I'll forever be grateful for the sisterly love we have for one another and will never forget the special moments we shared during the photoshoot in Punta Cana."
Graham honored Abigail on Instagram with a video, writing, "Couldn’t be more excited to have my stunning sister @abigailgrahamralston by my side in my new @swimsuitsforall campaign. Abby, we have been through it all together... from the late night phone calls and last minute vacations to tears and laughter navigating our way through marriage, babies and all that life has brought us. The best thing about it all is getting to do it with you!"