They are sons, they are grandsons, they are brothers and they are friends. As Australian drug smugglers Andrew Chan and Myuran Sukumaran face the unimaginably grim prospect of losing their lives to a firing squad, their families and closest friends begged for mercy from Indonesian President Joko Widodo in Sydney before accepting petitions for clemency from more than 150,000 Australians.

"I begged the President once before. This is the second time I have come here to beg pardon," said Sukumaran's wheelchair-bound grandmother, Edith Visvanathan, who on Sunday afternooon spoke with determination despite her physical frailty.

"I am asking for him to forgive my grandson and Andrew … I beg him again and again to forgive them and give both of them a second chance," said Ms Visvanathan, who was flanked by her nephew and great niece.

Damon Smith, a close friend of both Andrew Chan and his brother Michael, fought back tears as he implored the highest levels of the Indonesian government to grant a stay of execution and thanked campaigners for their support.

"Andrew is our son, Andrew is our brother, Andrew is our friend. We love him and are so proud of his transformation," said Mr Smith. "We simply ask that Andrew be allowed to live so that he can continue the work that he started inside Kerobokan [prison] with the support of the Indonesian prison system."

"A lot of people have asked how Andrew is," Mr Smith added, his voice breaking. "He continues to pray, continues to smile and continues to follow his love of rugby league and his beloved Penrith Panthers."

The family members asked for the public to continue showing their support by signing the online petition.

While last-minute, fevered legal work is being carried out in Bali to try to avert the deaths of the young men who were sentenced 10 years ago for drug trafficking, momentum is growing for the Mercy Campaign both in Australia and around the world in the face of what campaign co-founder Matt Goldberg called "the most precarious, urgent and pressing scenario".

"So much more can be achieved by being merciful and compassionate than in the alternative: proceeding with an arbitrary killing," Mr Goldberg told gathered press and supporters at the headquarters of the Media, Entertainment and Arts Alliance in Redfern.

Both of the men's immediate families have travelled to Bali, where they are being given good access to the death-row inmates, Mercy Campaign co-founder Brigid Delaney said.

In a statement read at the Sydney event, Foreign Affairs Minister Julie Bishop said the signatures demonstrate a strong opposition within Australia to the death penalty either at home or abroad.

"We are pleading with the Indonesian government to show [Chan and Sukumaran] mercy," Ms Bishop said. "A decade on from their crimes, Myuran and Andrew are changed men … Their remarkable rehabilitation demonstrates why they must be given a second chance."

Earlier, Prime Minister Tony Abbott made a personal appeal to Mr Widodo to grant the men an 11th-hour reprieve.

Diplomats from Australia have been summoned to a meeting in Jakarta on Monday to discuss procedures for the imminent executions.

United Nations secretary general Ban Ki Moon has joined calls for Indonesia to call off the executions, underlining the UN's opposition to the death penalty under all circumstances.

Shadow minister for foreign affairs Tanya Plibersek echoed the pleas, calling upon the Indonesian President to show compassion.

"We oppose the death penalty for every offence, for everyone, everywhere," she said in a statement of support for the campaign.

"While there is life, there is hope. We will not give up."