What should I do about preventing my siblings from using the computer, fearing for them that they might go astray due to its use for games, movies, and songs, given that this prevention causes me beatings and punishments? And should I abandon them and remain silent about the reprehensible?

Changing what is wrong is obligatory according to one's ability, through advice, guidance, and directing brothers and sisters to what benefits them, and keeping them away from what is forbidden, such as singing and obscene films. If you are not harmed by removing the device from the house, then remove it. It is never permissible to remain silent about what is wrong for one who is able to remove it by a means that does not lead to falling into something worse. If you are unable to do all of that, then there is no blame upon you, for a person is not burdened beyond his capacity. Allah the Almighty says: "Allah does not burden a soul beyond its capacity."