Al is Tom’s younger brother. He is only sixteen years old. In this book, he is described as a person with the big obsession with cars and girls (now it can be typical for each third man in the Earth). Anyway, he remains combative toward the rest of the family.
Al’s character is vain and cocky. But nothing can be that much worse. He is an extremely brilliant and competent mechanic, and his expertise proves vital in bringing the Joads, as well as the Wilsons, to California. So, being responsible for the maintenance of the family's truck during the journey to California he grows on our eyes. It seems like now he is much better than he was before the trip.
Al always idolizes Tom. He adored him and tried to lead him everywhere anytime. However, living in his big brother's shadow can be a lot of pressure. That is why by the end of the novel he has become his own man doing things the way only he wants them to be done.
Also, some time ago he promises to marry one girl in Weedpatch, but things rarely go the way we want them to. One time, his family was working on the cotton plantation, and exactly there happened a very cute thing. He falls in love with a girl Agnes Wainwright and decides to stay with her rather than living with his family. Who knows if it was a proper move? Maybe for sixteen years old boy is too risky leaving family and to live with another one. We can’t judge if it was good or bad to run away from your beloved family, especially being an only sixteen-year-old boy. But let’s summarize – that period demands sacrifices and to be ready for them was a very important thing.
Al Joad in the Essays