sentences:  He was the bastard son of William Douglas, 1st Earl of Douglas and Margaret Stewart, Dowager Countess of Mar & Countess of Angus and Lady Abernethy in her own right.He was seen as the product of incest because his father had married Margaret, Countess of Mar, whose brother Thomas, Earl of Mar had married Margaret Stewart, his mother.His father's wife Margaret had already produced an heir for her Lord in 1358, James, 2nd Earl of Douglas and Mar, who succeeded his father upon his death in 1384.