Can you learn to sing through online tutorials? Is it possible to learn to sing (I don't have a good voice either) through online videos and tutorials? If yes can you suggest to me some of these courses/ tutorials?

Yes, it is possible to learn singing online. Online courses will help you understand the theory, but for effective development (and to avoid harming your health) you need a teacher. These days, online vocal lessons are just as good as offline, but much more convenient and often cheaper. Try mg.education, there are lots of free tuition materials freely available and sometimes they offer a trial lesson for free, so you can try both options.