Fan Casting Martian Manhunter

J'onn J'onzz is manhunter from Mars, who lives peacefully with his wife and daughter, until White Martians attack and civil war breaks out which all breaks down to almost all Martians perishing. J'onn then has to settle in his new home, Earth and to think should he isolate himself or protect his new planet, but then finds out that his pregnant sister and brother-in-law are also live and captured by US government and sets a plan to rescue them and try to find a way to prove to humanity that he is good