Mrs Josephine Teo and Mr Desmond Lee will be promoted to full ministers in the latest round of Cabinet changes, which observers say will consolidate the front bench of tomorrow.
Four ministers of state will also be promoted to senior ministers of state: Dr Lam Pin Min, Dr Janil Puthucheary, Dr Koh Poh Koon and Mr Chee Hong Tat. They will continue in their current ministries.
Dr Lam will also be appointed Senior Minister of State for Transport.
The changes are part of leadership renewal, the Prime Minister's Office (PMO) said yesterday.
They take effect on May 1.
Political watchers said the newly promoted ministers will add to and strengthen the core team of fourth- generation leaders. Said ISEAS - Yusof Ishak Institute research fellow Mustafa Izzuddin: "The Prime Minister and his generation of ministers are building a team that can provide the necessary support to the next PM so the next lap of Singapore's political leadership will continue to be a team effort."
Both Mrs Teo, 48, and Mr Lee, 40, will be ministers in the PMO.
Mrs Teo will also be Second Minister in the Ministry of Manpower (MOM) and the Ministry of Foreign Affairs, and will give up her appointment in the Ministry of Transport.
She will continue to oversee population matters, assisting Deputy Prime Minister Teo Chee Hean.
Mrs Teo's promotion means that for the first time, Singapore will have two women as full ministers in the Cabinet. The milestone was not lost on Minister for Culture, Community and Youth Grace Fu, currently the only woman Cabinet minister, who hailed it as "yet another step forward for women in Singapore".
Mr Lee will be Second Minister in his present ministries: the Ministry of Home Affairs and the Ministry of National Development. He will be one of the youngest full ministers in recent years.
Experts called this Prime Minister Lee Hsien Loong's way of enlarging and strengthening the pool of leadership, without throwing in the rookie ministers at the deep end.
"This is a cautious pace of leadership succession," said Institute of Policy Studies deputy director Gillian Koh. "You don't see the standing down of senior members of the Cabinet, and you have the youngest set double-hatting a lot."
Observers saw Mrs Teo's move as a sign that she may be groomed to be the next manpower minister, especially given her past experience working in the labour movement.
Mrs Teo herself said of her MOM appointment: "It feels like I'm coming home to Singapore's unique brand of tripartism at this critical juncture for our workers."
As for the new senior ministers of state, all have been in office for under three years: Dr Lam since August 2014, Mr Chee since October 2015, and Dr Janil and Dr Koh since January last year.
Observers say this steep trajectory signals that they could become ministers if they prove themselves.
Additionally, parliamentary secretaries Low Yen Ling and Faishal Ibrahim will be promoted to senior parliamentary secretaries in their current ministries: Trade and Industry, and Education for Ms Low, and Education and Social and Family Development for Dr Faishal.
Minister of State Sam Tan will take on the foreign affairs portfolio, in addition to his current ones in MOM and the PMO, while Parliamentary Secretary for Home Affairs Amrin Amin will take on an additional post in the Health Ministry.
Minister of State for Manpower Teo Ser Luck will step down from office on June 30 and return to the private sector, at his request. His term as mayor of North East District ends on May 26, but he will still be an MP for Pasir Ris-Punggol GRC. Tampines GRC MP Desmond Choo will replace him as mayor.
The four other mayors - Dr Mohamad Maliki Osman, Dr Teo Ho Pin, Ms Denise Phua and Ms Low - will be reappointed on May 27.