Which state is referred to as 'brother' to the seven states in the North East India?

Sikkim

The correct answer is Option (2) → Sikkim

In the North-East, regional aspirations reached a turning point in 1980s. This region now consists of eight States. Arunachal Pradesh, Assam, Nagaland, Manipur, Tripura, Mizoram and Meghalaya, which earlier constituted the North-East region, are often called “the seven sisters”. Sikkim, which has been added to the list is–referred to as the ‘Brother’ to those seven states. The region has only 4 per cent of the country’s population but about twice as much share of its area. A small corridor of about 22 kilometers connects the region to the rest of the country. Otherwise the region shares boundaries with China, Myanmar and Bangladesh and serves as India’s gateway to South East Asia.