That can happen with any naturally non-english parent and an english speaking parent, not just hispanic parents with half black kids. And it happens for various reasons. Ranging from the environment they are in to just pure laziness.-My oldest brother's wife is Mexican-American, her parents originated from Mexico. They never taught her Spanish so she can't teach my nephew even though she wants to.-One of my grade school friends is half black, half mexican her father never taught her or her siblings Spanish because he was teased as a child for having an accent.-Another grade school friend- both parents born and raised in Mexico- she only knows what she has learned in school because they felt that she should know English since she is in America.-My ex-roommate- her mother was mexican and her father is white and she barely knows Spanish, I know more than her.-opposite-Another grade school friend- She was half black and half Columbian and didn't learn English until starting middle school somehow.My cousin's African father never taught her "Nigerian"My brother in law hasnt taught his kids Irish Gaelic, even though it's a dying languageMy hubby was born in Italy by an Italian father and a french mother. When he left Italy at 4 he also left behind his knowledge of the language. He is fluent in French however.I think it would be great for non-english speaking parents to teach their kids their languages but if they don't they probably have a valid reason.