Final answer:
Duncan's second son who flees to Ireland after his father's murder in Shakespeare's 'Macbeth' is Donalbain.
Step-by-step explanation:
In Shakespeare's Macbeth, Duncan's second son who suggests to Malcolm that they should leave after their father's murder and eventually flees to Ireland is Donalbain. After King Duncan's murder, Donalbain and his brother Malcolm discuss their perilous situation and decide it is unwise to stay, as their lives are at risk. Donalbain chooses to escape to Ireland while Malcolm flees to England to seek support.