"So this was the best day of my life. 22nd of July 2020, I asked the love of my life to spend the rest of her life with me and she said YES," Greg wrote.
He continued: "Couldn't be happier and I love you with all my heart @ameliaspencer15."
Shortly afterwards, the stunning 28-year-old bride-to-be shared in her excitement as well.
"I couldn't love you more. Happiest day of my life!" Amelia wrote in the comments, along with several love-heart emojis.
While Amelia's own Instagram page is set to private, it's quite likely she would have shared her own announcement on her page with her following.
Proud father to Amelia, Charles Spencer, who is Princess Diana's brother also shared his own well wishes for the couple.
Taking to Twitter, he wrote: "So happy for my daughter, Amelia, engaged to her boyfriend of 11 years, Greg - it's wonderful to hear them both so excited about their future.
"Sending them both love, and every good wish for their life together. I love that Greg asked my blessing before proposing. Very sweet," he added.
This certainly isn't the first family member who'll soon be getting married either.
Indeed Amelia's older sister Kitty is also set to wed her fiancé Michael Lewis.
Lewis is a millionaire fashion mogul of the Jewish faith, and it's been reported that Kitty will convert to Judaism ahead of their nuptials.
The two sisters share two other siblings, Eliza and Louis (who is very easy on the eyes, might we add).
In another exciting addition to the news, we can't help but wonder whether this means the family's close cousins, Harry and William will attend both nuptials within the Spencer fold.
The families are reportedly close given their link with Princess Diana - and with the Spencer siblings all attending both William and Harry's own weddings in 2011 and 2018 respectively, it would come as no surprise to see them attend with their own wives Duchesses Catherine and Meghan.
We'll keep you up to date with any further announcement on wedding dates.