The Because of You singer and her talent manager fiancé are pictured in a romantic embrace, standing under a brick archway surrounded by leaves. Kelly looks every bit the fairytale princess in an off-white flowy dress with diamante-embellished capped sleeves.
"Okay... One more from our engagement shoot ha! #TieItUp :)," she tweeted, alongside the touching snapshot.
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The former American Idol winner has opened up about adjusting to her new role as soon-to-be stepmother to Brandon's young children, and has said she enjoys looking after them.
"I have a 12-year-old and a 6-year-old now after being single for six years," Kelly told Ryan Seacrest on the KIIS FM show. "We all live together and everything. It's so different, but it's perfect. They're awesome and I actually really dig the mom thing."
Kelly and Brandon are set to tie the knot on 20 October 2013, and the ceremony will be officiated by The Voice judge and country music singer Blake Shelton.
While Kelly has said in the past that she was nervous about the big day, the songstress has revealed the preparations have been "overwhelming".
"It's two months away. It's end of October," she said. "I'm so over it. It's so overwhelming. We're just doing a lot—touring and the wedding and the Christmas album, so I'm over the wedding part."
Kelly posted her first engagement photo last month in which she looked equally as stunning. The snapshot shows the pop singer modelling an extravagant wedding dress and leaning back against a window, reading a book in a library.
Kelly chose her actual wedding dress, by designer Vera Wang, back in February.
"It is my personality in a dress," she said. "It's sweetly damaged. A little rock'n'roll. A little tattered. Nothing like a princess thing!"