Cena and Bella began dating in 2012 and Cena proposed to her at the 2015 WrestleMania but they split up in July 2018.
The Total Bellas star said at the time: "After I called off the engagement, we tried to work on our relationship to get back to where it was, and in order to move forward with our wedding.
"After much time and soul-searching alone and together, we have decided to officially part ways.
"I had a beautiful and loving six-year relationship with a wonderful man. I have the utmost respect for John, but I know this is what’s best for me."
Now 36-year-old Nikki is engaged to her Dancing With the Stars partner Artem Chigvintsev.
She wrote: "Excited for 2020 and the next decade with you @theartemc. I said yes in France in November!
"We have been trying to keep it a secret but really wanted to share our excitement for the New Year!"
Artem, 37, also posted on Instagram about popping the question to the retired wrestler writing: "You are the best thing that has ever happened to me.
"So excited for what's to come I love you more than anything and thank you for saying Yes."
And it seems both Cena and Bella moved on quickly from their public break-up, with Cena striking up a relationship with engineer Shay Shariatzadeh, who he met when he was filming Playing with Fire in her native Canada.
A source told that the former WWE 'it' couple see their past as all water under the bridge.
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They said: "John is very happy for Nikki and her engagement.
"He is very happy that she has found someone that treats her so amazingly well.
"Nikki was an extremely important part of John’s life so it does remind him of what they had and he is also reminded of his proposal to her at WrestleMania a few years ago but he also has thought that they have both grown from their relationship and they both have moved on."