One parent, one language: The first rule in raising a bilingual child is to ensure that the same language is maintained by the same parent. This is known as the ‘One parent, one language’ approach.
Sticking to this rule may be difficult if one of the languages is spoken in the country in which you live. For example, if a mother is French and the father is Spanish and the family lives in Spain, Spanish will be learned with greater ease for the child. Therefore, experts say that the mother in this situation must find at least 25 hours a week wherein the child is exposed to French in order for fluency to develop.