@ damian_wayn, I don't know if I'm too late but I'll just try it.
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First of all: It's totally okay when you don't have finished a story! I also fantazise a LOT (a year ago) and wanted to write it in books (here on Wattpad) and I didn't even finish a chapter! I'm a slowly writer but still.
My English is not good, so there may be grammatical/-spelling mistakes. I only have DC-Comics ideas but I hope I could help you.
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-Maybe you can write a story where Batman is not a good father for Damian?
-A story where Jason and Damian are living together (not as a couple, but it's your story, so you have to decide)
-A story where Dick is the one who plays "the older brother" and helps his little siblings with their stuff?
Like, Damian needs help with his homework and Dick helps him. Or Timothy needs someone who would go on patrol with him to hack computers and Dick team up with him.
-A story where all the Batbrothers are grown up and it's time for the next generation? Or a story, where the sibling are all kids? Or even Reverse-Batfamily?
-A story where Tim suspect that the family hides a secret, which he doesn't know? So he tries to find it out but in the end he gave up and then it turns out, they just planed his birthday-party?
(You can choose another end; I just didn't know what should be the end, so I chosed the "Planning Tim's Birthday-Party")