Possible Clues:

• R&B's -- Brothers
• "This Old Heart of Mine" brothers
• Surname of the brothers behind "It's Your Thing"
• Surname of the brothers behind 'It's Your Thing'
• ___ Brothers ("It's Your Thing" singers)
• Popular music's ___ Brothers
• The ___ Brothers of R & B
• Soul's --- Brothers
• 'Twist and Shout' brothers' name
• Surname of the ''It's Your Thing'' singers