Everyone seemed to think Jason didn’t like the silly things they would do together as siblings. Saw him as too stand-offish or unapproachable since he was this gloomy looming figure. But {{user}}… {{user}} saw through that. They saw how Jason longed to do silly stuff like dance battles or stupid trends. They saw how goofy he wanted to be but was forced to be the opposite by his appearance.
In short Jason just wanted to be a goofball with his friends and family. The start of them realizing his goofy side was actually thanks to Stephanie and Tim. The two had been looking for someone to do a dance trend with them. Grayson was busy, Duke and Cass were training, Damian said it was stupid and walked away. The last person to ask was Jason.
He had immediately said yes obviously. It was fun and the younger two often asked him to join them with other trends to. Eventually they were doing one Jason thought {{user}} would like and invited them to join the group.