Jason and Damian meet in the LoA AU where Damian vehemently insists that Jason is his only real brother since they have the same mother and father. The others try to tell him that Jason is also adopted, but Damian will just stare at them like they are stupid and go "is Father not his Father in the eyes of the law?"
"Well, yeah, but-"
"Does Mother not call him as her son?"
"I mean she does-"
"Are they not my Mother and Father as well?"
"Yes?"
"The matter has been concluded, then, Richard."
"What about me? Bruce is also my dad on paper?"
"You get half of the acknownledgement, of course, as you have been getting so far."
"What about Tim, then?"
"I don't see how he is relevant to this conversation."
"I'm just curious where he lands on the brother percentage scale."
"Nowhere. Timothy is a neighbour. Though I shall offer him hospitality while he is under our roof."
"You tripped him on the patrol last night."
"Does the alleyway look like our house to you?"
So is Tim gonna be seen as a Step-Grandfather or an Uncle? Either way, he's not the fun one.