Related Clues:

• Foreign agreements
• Marcia, to Greg
• A sib
• Serena, to Venus
• Bridget to Jane
• Bro's sib
• Family nickname
• Nephew's sister
• Criminal
• Affectionate family name
• Cheer opener
• ''--- boom bah!''
• Palindromic sib
• Familiar sibling title
• Austen's Jane Fairfax, for one