Complex sentence: John Mor MacDonald was the second son of "Good" John of Islay, Lord of the Isles, 6th chief of Clan Donald, through John of Islays second marriage to Princess Margaret Stewart, daughter of King Robert II of Scotland.
Split into simpler sentences: John Mor MacDonald was the second son of "Good" John of Islay, Lord of the Isles, 6th chief of Clan Donald. Through John of Islays second marriage to Princess Margaret Stewart, daughter of King Robert II of Scotland.