Complex sentence: Feodora suffered from a lifetime of ill-health, believed to be porphyria inherited from her maternal great-great-great-grandfather George III of the United Kingdom, after recent medical tests were carried out on her remains and those of her mother.
Split into simpler sentences: Feodora suffered from a lifetime of ill-health, believed to be porphyria, inherited from her maternal great-great-great-grandfather George III of the United Kingdom. That diagnosis followed medical tests carried out on her remains and those of her mother.