You all know Damian Wayne. Biological son of Bruce Wayne. You all know Terry McGinnis Batman of the Future. You may or may not know one thing. Terry McGinnis is actually the biological son of Bruce Wayne. It was shown in the last episode of Batman Beyond.
So Damian and Terry are bros. I wish Damian was created in the 90's so we could see the relationship between them. Who knows maybe it will show up in comics one day.