Complex sentence: It is assumed she inherited the disorder, if indeed she had it, from her father, James V of Scotland; both father and daughter endured well documented attacks that could fall within the constellation of symptoms of porphyria.
Split into simpler sentences: It is assumed she inherited the disorder, if indeed she had it, from her father, James V of Scotland. Both father and daughter endured well-documented attacks that could fall within the constellation of symptoms of porphyria.