Does the cost of repairing a company car fall under the company's accounts if one of the brothers paid the required amount for the repair without it being a loan?

The intent of the question is unclear. However, if the question is whether you can claim back the cost of car repairs from the company, then:

If the repair is due to your transgression or negligence, then the responsibility for the repair falls on you, and you cannot claim it back from the company.

If the repair is due to authorized use without negligence on your part, then the responsibility for the repair falls on the company, and you are entitled to claim back what you have paid.

As for what your brother gave you as a gift, it becomes yours upon taking possession of it, unless he stipulated that it be used for car repairs, or he gave it to you to cover the cost of repairs, and it becomes clear that the repair is the company's responsibility.