Most casinos allow multiple people within one household or family to create an account. But they must be actual different people, because each casino only allows one account per person. In the case of multiple players per address or IP address, the casino requires that all account holders provide identity information. If every person is of age, has his own e-mail address and pays via his own name-linked payment method, in most cases there is no objection that they all create an account separately.
Although having seperate accounts is the best way if you and others in youre house like to play casino games, there can be a downside to it. Some casinos only offer one bonus per IP adress. This is to prevent misuse. It's not the case with every casino and there is a difference between bonuses and free spins. Make sure you check the terms of your casino for multiple account conditions. If they are unclear about this, contact the helpdesk.
That said, some casinos want to make sure it's not one person that has serveral accounts. So, it can be a good idea to contact your casino anyway and let them know you have seperate account holders at one ip adress.