Complex sentence: Robert Maxwell, 5th Lord Maxwell (1493-1546), Was the Lord of Maxwell Family/clan the Maxwell's were a minor house of the royal House of Stuart (through the marriage of Robert to his second wife Lady Agnes Stewart).
Split into simpler sentences: Robert Maxwell, 5th Lord Maxwell (1493-1546), Was the Lord of Maxwell Family/clan. The Maxwell's were a minor house of the royal House of Stuart (through the marriage of Robert to his second wife Lady Agnes Stewart).