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jessica2477: I had to give this much thought, now be warned any ideas I spout out are quickies that are open to change however we see fit.
1) We could go the sibling and god route and maybe use Apollo and Artemis, or other gods of our making. I had this one idea about one of the gods being sealed away by the gods, they feared with his growing power he would take over Olympus. The island he was sealed away on was lost forever and rediscovered in the modern age by an anthropologist. Somehow she/he manages to free the god, the god is weak after the long imprisonment and burns with revenge against the other gods. He starts to get his powers back day by day and comes up with a plan of revenge. Our sealed god doesn't just want to take over, he wants to destroy the other gods entirely.
2) Warring nations and siblings. Two nations have been in a power struggle for many a year, the king of one nation has two children born a couple years apart. The rival nation steals the eldest son as a toddler and raises him as their own. A certain amount of years later the king is ailing and has only a daughter to succeed him. But that will not be allowed without her taking a husband (there's an arranged marriage mixed in lol), the two nations are now at war. The brother has been raised as a crown prince of the rival kingdom, the two siblings eventually meet. That's all I have so far.
3) Orphan, split personality, horror. Alright a pair of orphans were adopted by a nice couple. One of the orphans has MPD and one of his/her personalities is sadistic and enjoys tormenting its new "sibling". I haven't thought too deeply into this idea but I did give a vague idea we could expand upon if you want this one.
Other then that just basic overused student/teacher ideas and royalty/commoner ones. Though if none of the above interests you I can think of more.