For many families, bilingualism is determined by having two parents with different L1s. It is always the right choice to raise children speaking the languages of both parents/families. I sometimes meet adults who were raised as monolinguals, with one of their parents choosing *not* to speak their L1 with them. And I can say that every one of these adults I have met has expressed regret about not being bilingual, and sometimes even greater regret at not feeling a part of the culture of one of their parents. This usually happens with immigrants – they feel that their children need the majority language (usually English) rather than a heritage language, and raise their children accordingly. Sometimes, the value in a language is not only in being able to speak it with others, but to use it as a door into a culture. When we live apart from one of our cultures,  the easiest access we have to that part of our identity is through the written word, or through traveling to meet family. Without the language to do that, people can be left feeling isolated from a part of their own identity. So the easy answer, for bilingual families, is that the children should be raised bilingual, speaking the languages of both the parents. The usual paradigm for this is called “One parent, one language” (OPOL) and it is one of the most successful paradigms for non-societal bilingualism. If you have raised your children this way, I’d love to hear about challenges and wow moments along the way!