Diddy might be spending Father’s Day behind bars at MDC Brooklyn … but, his kids are still sending him their best — sharing loving posts amid his federal trial.

Justin Combs posted for his dad late Sunday afternoon … sharing what looks like a behind-the-scenes video of Combs at a group meeting — with Diddy telling the camera it’s a proud day for him.

Diddy seems to be speaking to Justin, Christian Combs and Quincy Brown — Kim Porter‘s son who he adopted — who are listening intently to their dad.

Diddy’s trial is rolling on in New York City … with the 24th day of testimony set to begin tomorrow as he fights off sex trafficking and other federal charges.

The trial’s been full of twists and turns — both in the courtroom and in the overflow galleries where Kanye West made an appearance last week — and, the verdict is still very much up in the air at this point.