Walker, who died in a vehicle accident in 2013 at the age of 40, was very close with Diesel, as were their families.
In the pic, Meadow, 21, stands with Diesel's three kiddos - Hania, 12, Vincent, 10, and Pauline, 5 - all with smiles on their faces.
Fast & Furious co-stars Nathalie Emmanuel and Gal Gadot were quick to show their support, with Emmanuel commenting, "Miss you all".
A coroner's report ruled that Walker died from the trauma of the crash as well as being burned when the vehicle caught fire.
Hollywood actors Paul Walker and Vin Diesel had always shared a great rapport and friendship.
But while many years have passed since the fateful accident, Vin still sees his fellow actor as a "brother", having celebrated what would have been his birthday last year with a heartfelt Instagram post that said: "Normally today I would be planning how to embarrass you with a birthday cake". The tears never go away, but they change. from that of mourning to that of grace.
In addition to these important symbolic gestures, the two families have frequently given each other public shoutouts, such as when Vin shared an endearing happy birthday message to Meadow on her 21st and when Meadow posted a picture with Vin's daughter Hania, captioned "with my angel".
This isn't the first time that the friends have shared their time together on social media. "Love you kid. Uncle Vin". But it felt right.