Some Jason fanfics I've come across lately (other than ithoughtslashmeanthorror's ongoing).
Come Alive: Takes place in season 3 of Young Justice. Up until the episode where the Outsiders are on Infinity Island. Partially about baby Damian, but most of it is about Jason.
https://archiveofourown.org/works/17...pters/41103026
Frozen History: The adopted kids of Bruce are all de-aged to 10 (Damian is still 10), with no memories of anything that happened afterwards. Barring certain circumstances (which is explained). Some excellent character interactions between all of them.
https://archiveofourown.org/works/12...pters/27629028 (admittedly, a Bat family one, but some really good character interactions all around).
Finding Jason: AU of Rebirth Red Hood and the Outlaws, with a little girl popping up several years after the Outlaws (barring Starfire) have gone missing. Including Jason. Said girl, Carrie Kelly. A mystery of what happened to them, as in this series, Roy himself has Lian (though she wasn't with them). 3 chapters, but very interesting thus far.
https://archiveofourown.org/works/16...pters/39286078