The finalists from last year's series have become the latest to part ways, just days after Megan Barton Hanson announced her split from Wes Nelson.
Kaz took to Instagram to reveal that she and Josh were no longer together after meeting in the villa last summer.
She shared a picture of herself and Josh looking loved up, but captioned the snap: "Sometimes things don’t go the way you planned, but you have to be grateful for the journey. Thank you for everything especially showing me how to love myself again ❤️"
Josh responded to the post with an unhappy face and pray hand emojis.
Their fellow Love Islander Wes posted: "Stay positive! Nothing but love for both of you guys [heart emoji]."
Dani Dyer, winner of the 2018 series with Jack Fincham, added: "You'll never forget the perfect summer."
And Hayley Hughes, who also appeared on Season 4 last year, reacted: "Nooo my fave couple"
Kaz and Josh's separation follows Wes and Megan's break up at the weekend.
Megan posted about the split on social media: "I am so grateful and so blessed to have found Wes, I will always love and adore him and I am so lucky to call him my best friend," Megan continued.
"It has been an incredibly hard decision to make for both of us but we are looking forward to moving on together as friends and supporting each other in everything we do."
The only Love Island couple still together from last year's final at this time are winners Dani Dyer & Jack Fincham.
There's also Adam Collard and Zara McDermott, who have remained a couple despite being eliminated from the villa halfway through the show.
Love Island will return for what will be a fifth season this summer on ITV2.