Heredity plays a major role in certain language problems. Therefore, children with an older brother or sister with a developmental language disorder are more likely to have language problems. This is especially true if the older sibling has a disorder that manifests itself in a delay in grammar, sentence structure, and sentence formulation. This is reported by the Kohnstamm Institute.
A lagging vocabulary does not entail an increased risk of developing language problems in a younger brother or sister.
