This author Rodriguez argues that when a bilingual family makes English their primary language they lose a but of who they are. He describes English as being a public language and Spanish a private one. Implying that being able to speak Spanish is what makes his family different, and they can have that private connection with one another without worrying about the rest of the world. But after being forced to learn English as their primary tongue they are being more connected with the outside world and losing that private connection they once had with one another.
He feels that speaking Spanish is what held his family so close, and having to learn English pulled them apart. The children now speak English a lot better than the parents and are often misunderstood, so to aviod that they simply rarely talk to their parents at all anymore. Then the father lost his head of the household role by not being able to speak English as well as his wife, so now just remains silent most of the time and lets her control everything.
Pretty much it seems that Rodriguez feels that learning English is what has teared his family apart.