I am confused, do i have to pay 30$ for a new MC account if it is already on my computer? I am wondering because me and my sibling share the current account.
You can share the same account onto multiple PCs, but only one person can be logged in at one time. If someone else logs-in on the same account, they will be able to still play Single Player (No LAN), but cannot join any multiplayer sessions. (This includes opening your Single Player world to LAN; the other player will not be able to access the "server" since the host and the person joining are the same account).