1.hermano / hermana
• 2. casado / casada
• 3. yerno / esposo
• 4. abuela / pez
• 5. nuera / yerno
• 6. sobrino / sobrina
• 7. niño / mascota
• 8. pájaro / hermano
• 9. suegro / suegra
• 10. novio / novia
• 11. tío / suegro
• 12. nieto / yerno
which of these pairs does not belong?
Are they the only instructions you got?
Assuming that people should stay together, I'd say the following:
4. grandmother and fish
7. child and mascot
8. bird and brother
Sra