Two brothers remained out of Singapore without a valid exit permit and failed to report for national service for more than five years and more than three years respectively, a court heard.
But they went on to serve their full-time NS exceptionally well - one was selected for Officer Cadet School, while the other won a Soldier of the Month Award.
On Tuesday, Sakthikanesh Chidambaram was jailed for three weeks. His brother, Vandana Kumar Chidambaram, was fined $6,000.
Sakthikanesh, 25, pleaded guilty to one charge of failing to report for NS for five years, six months and 17 days.
Vandana, who turns 23 in two weeks, pleaded guilty to one charge of failing to report for NS for three years, six months and two days.
Both admitted to another count each of remaining outside Singapore without a valid exit permit.
The prosecution, which had asked for short jail terms, intends to appeal for stiffer sentences. Defence lawyers had asked for fines.
A district court heard that the brothers' Singaporean mother settled in India after she married an Indian national in 1990. But she came back to Singapore to deliver her sons in 1991 and 1993. About two months after each boy was born, their mother took them back to India. They grew up there and attended the Delhi Public School.
The boys visited Singapore six to seven times between 2000 and 2009, with each visit lasting over a month. Both renewed their passports twice, and applied for and got their identity cards in 2006 and 2009 respectively.
In June 2008, Sakthikanesh was told to register for NS. But he left Singapore later that month to pursue his university education in India, returning only in April 2014, after completing his studies. He enlisted for full-time NS in September 2014.
In May 2010, Vandana was told to register for NS. He, however, returned to Singapore only in June 2014 and enlisted for full-time NS in August 2014.
District Judge John Ng found the brothers had "a substantial connection to Singapore". He noted that both got their ICs and used Singapore passports for travel, and that their mother co-owned a Housing Board flat.
The judge said: "If the circumstances showed that the offender (or his parents) had demonstrated all along an intention to retain his Singapore citizenship, it behoves upon him to discharge his NS obligations... at a time when other male Singaporeans are asked to report for NS, and not be allowed to perform his duties only at a time that is convenient to him or of his own choosing."
But the judge noted, among other things, that both men had performed their NS duties exceptionally well. "Sakthikanesh did so well in basic military training... he qualified for Officer Cadet School (OCS). He had almost finished the OCS course to become a commissioned officer when he was suddenly and devastatingly deprived of that opportunity, due to being charged in court...
"As for Vandana... based on the testimonial he had received from his superiors, as well as his solid performances, he was chosen to be an Armoured Vehicle Gunner for the SG50 National Day Parade and he was also named as his Company's Soldier of the Month for May this year," said Judge Ng.
For their Enlistment Act offences, Sakthikanesh and Vandana could have been fined up to $10,000 and/or jailed for up to three years.
Deputy Public Prosecutors Kumaresan Gohulabalan and Randeep Singh Koonar prosecuted the case. Straits Law Practice's Mr Tan Jee Ming and Mr S. Balamurugan defended Sakthikanesh and Vandana.