Complex sentence: Unlike her two sisters-in-law, Mathilde and Astrid, Claire has no defined official role, though she occasionally appears in public accompanying her husband, generally in support of environmental causes or animal charities.
Split into simpler sentences: Unlike her two sisters-in-law, Mathilde and Astrid, Claire has no defined official role. She occasionally appears in public accompanying her husband, generally in support of environmental causes or animal charities.