Marcelas, now 13, still hopes the law to which he has dedicated his short life will live on, as its constitutionality is being challenged this week before the Supreme Court.
"It's something that a lot of people could benefit from and my family's benefited from," Marcelas told ABC News. "Even though I don't want it to be taken away, I think [the Supreme Court challenge] could open some people's ears to this situation and might change their minds."
Marcelas, a seventh-grader from Washington State, was the youngest person at the table when Obama signed the Affordable Care Act in 2010. That day was the culmination of two years of work for the youngster, who, at the age of 8, vowed to carry on his late mother's legacy in health care advocacy.
"I believe that when people die, they have their legacy and working for equal rights was my mom's legacy," Owens said. "So since she started working on health care, I did too."
Marcelas' mother, Tifanny Owens, 27, died at age 27 of pulmonary hypertension in 2007 after three years of fighting for health care overhaul. The incurable heart disease, which caused swelling and took away her ability to walk, caused her to lose her job as an assistant manager at Jack in the Box. And with her job went her health insurance.
"When she lost her health care and she couldn't see her doctor anymore, there was no way for her to get the medication she needed," said Tifanny's mother Gina Owens, who now cares for Marcelas and his two sisters.
Because her salary for the previous year was too high, Tifanny did not qualify for Medicaid, the government insurance program for low-income earners.
"That, I think, was a flaw in the system," Gina Owens said.
Shortly after his mother died, Marcelas was determined to continue the fight she began: ensuring that all employees were given health insurance, not just managers, Gina said. Marcelas met with Washington state lawmakers, wrote letters to legislators and, eventually, caught the attention of Washington Sen. Patty Murray, who took his story to D.C.
As Congress geared up for the health care vote, Marcelas came to Washington, D.C. He walked the halls of the Capitol and the corridors of the White House telling his mother's story, asking lawmakers to vote in favor of the bill he said "a lot of people could benefit from."
"He didn't stop until he saw it passed," his grandmother said.
Now that the law is under the microscope again, Marcelas said he's "frustrated," but that he will keep fighting.
"I think there's always going to be someone who doesn't agree and wants to fight against it," he said, adding that even if the Supreme Court upholds the law, "we are still going to have to defend it."
As for Marcelas, he said advocacy might not always be in his future.
"I'll probably do that a lot, but, well, I have two different jobs that I want; one is a more realistic job and one is my dream job," the teen said. "The realistic one would be dealing with law or justice or writing, like a journalist maybe."
"My dream job," he said, "is being an entertainer and having a TV show. I like making people happy and laughing. [It would be] something like where if you had a bad day you would turn it to that."