From Nehru to Priyanka, journey of the Gandhi family in the Congress

New Delhi, Jan 23:The Nehru- Gandhi family has played a crucial role in Indian politics. When it comes to their family, Congressmen offer a strange formula: three is equal to one. There is complete unity in the trinity of UPA President Sonia Gandhi, Congress chief Rahul Gandhi and his younger sister Priyanka Gandhi. And Priyanka's formal entry into Congress leadership has only strengthened Sonia's or Rahul's roles at the helm.

Here are the key things to know about India's most famous political family:

The Nehru-Gandhi family has dominated Indian politics since independence from Britain in 1947, when Jawaharlal Nehru became the country's first prime minister.

Of the 15 people who led the 132-year-old party post independence, four belonged to the Gandhi-Nehru family. Long before independence, his great-great grandfather, Motilal Nehru, headed the party, the first from the family to do so.

The Nehru-Gandhi clan was at the helm of affairs of the party after independence for 38 years: Nehru for three years, Indira Gandhi and Rajiv Gandhi for eight years each, and Sonia Gandhi for a record 19 years.

Indira Gandhi held the post in 1959 and 1978-84, her son Rajiv Gandhi in 1984-91 and daughter-in-law Sonia Gandhi, from 1998 till date.

The dynasty has produced three prime ministers and a member of the family has been in charge of the country for nearly 50 of the 70 years since independence.

In 1984, Nehru's only daughter Indira Gandhi was assassinated by her Sikh bodyguards when she was prime minister, following a deadly confrontation between Indian security forces and Sikh separatist militants at the Golden Temple in Punjab state.

She had groomed her younger son Sanjay to be her political heir, but he was killed in 1980 when the small plane he was piloting crashed.

Her eldest son Rajiv reluctantly took over her political mantle, and served as prime minister from 1984 to 1989. He too was assassinated in 1991.

The Nehru-Gandhi family's decades-long dominance of Indian politics began to diminish in the late 1990s with the fortunes of the Congress party.

After Rajiv's death, the party was not led by a member of the Nehru-Gandhi family for several years, but in 1998, Sonia Gandhi agreed to take over.

She propelled Congress back to power in 2004 and ruled behind the scenes for 10 years. But in 2014, the party was routed by the right-wing Bharatiya Janata Party following a string of corruption scandals.

Rahul Gandhi is the fifth member of the Nehru-Gandhi family to lead Congress.