The present study provides evidence that individuals who have different patterns of cerebral lateralization and who develop along different maturational time courses can attain comparable levels of language proficiency. Right-handed individuals with left-handed family members (left-handed familials, LHFs) showed a shorter sensitive period for language acquisition than did right-handed individuals with only right-handed family members (right-handed familials, RHFs). The shorter sensitive period for LHFs may be due to a focus on non-linguistic, word-based conceptual information during language acquisition. RHFs may focus on grammatical relations during language acquisition, which matures later than lexical knowledge. This suggests that there may be different patterns of cerebral lateralization for language in all normal populations as a function of familial handedness.