This isn't the first time the couple have sparked engagement rumours.
Back in July for their two year anniversary, the Beauty and the Geek host shared her own post dedicated to Joshua with a not-so-subtle hint.
"Happy anniversary @joshuargross," she wrote at the time.
"I can’t believe you’ve put up with me for 2 years. I love you so much and you’re my best friend in the world... I can’t wait to marry you (hint hint)."
Sophie and Joshua are also celebrating Christmas together and shared footage of themselves decorating their tree together.
However, there was a little disagreement over the colour.
Captioning the video, Joshua wrote: "Soph wanted white, I wanted green. We compromised. We went with white."
But the former Bardot singer had to fight her corner and replied: "Back me up here team! Our entire house is only white."
The couple met on a business class flight and after a few champagnes, the former Bachelorette even leaned in for a kiss.
"I just sat down and he had a sense of humour and I was like, 'Oh, how relieving, sitting next to someone you can have a chat with'," Sophie told 9Honey.
"It was like, 'Good sense of humour, hard worker'… it just happened."
She also revealed that her relationship with Joshua is "the best" and that she can't wait to be married to him.