Final answer:
The decline of fraternal polyandry in Nepal is due to socio-economic changes including education, urban migration, and global cultural influences.
Step-by-step explanation:
In Nepal, the erosion of fraternal polyandry is attributed to several socio-economic changes. This practice, where brothers marry a single wife, was traditionally advantageous in rural Nepali societies due to land scarcity and the need to limit population growth. However, various transformations such as increased access to education, urban migration, rising individualism, the influence of global culture, land redistribution policies, and modernization have challenged traditional customs and led to a decline in fraternal polyandry.