Ok so I need someone to help cause I'm clueless when it comes to this & the guy from the agency…

Ok so I need someone to help cause I'm clueless when it comes to this & the guy from the agency didn't know how to help like if it wasn't his job... So my mom put my brothers car under her insurance along with ours that already been on before his & he didn't have have to pay because it was already paid for whatever is left of the month which was the payment I made last month until the 16th of this month.. Meaning he'll have to pay his part this month along with me.. Am I right ?