It is a long shot..........
Have you looked on the freebmd index to see if you can find his birth registration details, that at least could give you what quarter and area he was registered in, although I doubt you could obtain his birth cert, if you could find that and apply for family history purposes maybe, by stating on that on the form and your relationship as sister.
FreeBMD is only really complete up to the mids 1960's.I'd be very surprised if you found any births from the 1990's on there yet.
Maybe you could look into your dad's family,did he have any siblings,are his parents still alive?
Do you have an address that he was living at when he died? There might be some clues in the electoral rolls at that address.
All very difficult ,as Dawn says, when Rootschat is really meant to help with finding ancestors,and not living relatives.
Carol
His family is alive but they knew less about him than I did. A lot of his family tried to deny him. My mom said the same thought was of me as well even though I think anyone who saw him can obviously see I'm a lot like him in looks. However since when he was a baby he didn't look at all like my dad his mom's claim that he was his child was questioned and therefore I don't think he was ever seen as really family. I always say I have a brother because as far as I know I do. I just want to know if he actually exists if he's still around. But I can't go by my dad's family as they know very little about him. I know his name which is something I don't think many them even know.