Last year's protests were triggered by a proposed extradition law that would have allowed suspects in Hong Kong to be sent to the mainland.
Some of the relatives recently received handwritten letters from their loved ones for the first time since their arrest.
Hong Kong reported 43 new coronavirus cases on Saturday, including 13 untraceable local infections.
This is the fifth time Air India's flights from India have been banned by the Hong Kong government for bringing passengers who tested positive for the viral infection after arrival.
The pro-democracy camp announced their decision in a news conference Wednesday, hours after the Hong Kong government said it would be disqualifying four pro-democracy legislators.
Media groups are concerned Hong Kong's new security law, which outlaws secession, subversion and foreign collusion to interfere in the city's internal matters.
Media reports in Hong Kong, including from the South China Morning Post, said that the four lawmakers would be accused of filibustering meetings and violating their oaths of office.
Hong Kong was wracked by protests last year demanding fully democratic elections and opposing China's expanding influence in city affairs.
Lam said the meetings, set for Wednesday through Friday, will include discussions on how Hong Kong can integrate into China's national development.
Tony Chung, 19, appeared in court two days after he was arrested by plainclothes police in a Hong Kong coffee shop opposite the US consulate
The three include former Student localism leader Tony Chung and former members William Chan and Yanni Ho. The arrests of the three were confirmed on the now-disbanded group's Facebook page.
In the crowd in Taipei on Sunday were activists from several Taiwanese organizations, as well as other residents of the self-ruled democratic island.
Around 300,000 people currently hold a British National Overseas passport, while an estimated 2.9 million people are eligible for it, according to the British Consulate General in Hong Kong.
Hong Kong has no extradition agreement with Taiwan and Hong Kong's leaders say there are currently no laws allowing them to cooperate with Taipei's investigators.
In June, Cathay Pacific raised 39 billion Hong Kong dollars (USD 5 billion) in a recapitalization plan that gave the city's government a stake of about 6 per cent in the airline.