AOA, brother you can go on your brother's car for Umra. But you have to follow the procedure which is as under.

1. Your original driving license
2. Vehicle Istamara.
3. Authority Letter in Arabic.

Go to Customs office on corneache road near dewani Ameeri. Go inside and fill a simple form and pay 20 riyal fee for authorization letter from custom department. It will take only 15 mins.
give me your e mail id i will send you the format of authorization letter and also i will send you the complete road guide from Doha to Makkkah and to Madina.
TAke CAre and Allah HAfiz