Hmmm, this is an interesting question. In reality, I think it is unanswerable just because each life touches so many other lives; however, in the context of this novel, I think we can safely name some general "families" that are affected in the barrio of Buried Onions.
Considering the main character's name is Eddie, many of the effects center around him. Eddie himself (and his family) is affected by his father's death. Eddie's family and friends are affected by Eddie's cousin's death so much that they encourage Eddie to seek revenge. The white man that Eddie works for in landscaping is affected when Eddie works hard for him, but then accuses Eddie of stealing a truck. In actuality, the families in the barrio are so very interconnected that ALL of them are affected in the story. Eddie finally sees that his only hope is escaping the barrio of Fresno altogether.
The black asphalt would shimmer with vapors I had a theory about those vapors not released by the sun but by a huge onion buried under the city. This onion made us cry. I thought about the giant onion, that remarkable bulb of sadness.
In conclusion, we should say that Eddie's idea of joining the military at the end of the book shows a whole new level of interconnection of families. For if Eddie joins, there are many other friends he will make and many more families affected!