Young Brothers Orphaned in World’s Worst Tsunami Were Taken in by Their Neighbors: 'Made Us Who We Are' (Exclusive)
"Knowing that we are still here and together, more importantly, would be some comfort," Louis Mullan tells PEOPLE
Louis Mullan and his younger brother Theo were on vacation in Thailand on Dec. 26, 2004, when the world's deadliest tsunami slammed into them — killing their parents
Back in England, thanks to the kindness of a neighbor, the boys were taken in and raised with "love"
"If we didn't have that, I think that's when [life] would've been so much harder," Louis tells PEOPLE in this week's issue
Louis Mullan and his brother Theo returned home to the U.K. in shock after their parents vanished when the world's deadliest tsunami in history slammed into Khao Luk, Thailand, on Dec. 26, 2004.
About a month later, the couple was found dead — two of nearly 230,000 people killed in the devastation triggered by a 9.1 magnitude earthquake off the coast of Indonesia.
"Flying home without your parents and not knowing anything, but obviously [we had] common sense what the reality probably is," Louis, who is featured in National Geographic’s Tsunami: Race Against Time (streaming now on Disney+ and Hulu), tells PEOPLE in this week's issue.
But back in Cornwall, England, the boys, then 16 and 12, received an unexpected offer: a neighboring family of four offered to take them in. (Theo was even adopted due to his age.)
Although they hadn't really been close before tragedy struck, Louis, 36, still remembers when the family's mom, Linda, "sent us a card and said, 'We'd love to offer you a home.' "
"She felt something was telling her that she had to do that," he adds.
That decision, which allowed them to stay about 8,000 feet in proximity to their childhood home, also gave the boys the ability to "pretty much slot back into pre-tsunami life," he adds. Although Louis says there was "obviously some disruption," life carried on, which he's grateful for.
"If we didn't have that, I think that's when it would've been so much harder," he says. "The opportunities they've offered us and the love that they've given us has made us who we are."
Today, Louis runs a veterinary business with his wife Rachel, who is pregnant with their first child. Meanwhile, Theo, 31, works in media sales and is happily married, too. The brothers remain as close as ever.
For more on life 20 years after the 2004 tsunami, pick up the latest issue of PEOPLE, on newsstands Friday, or subscribe here.
And though 20 years have passed, Louis says he and his brother's grieving continues especially as they reach different milestones in life.
"When I got married, I was like, '[I] wish my parents were here to see this or to meet Rachel,' and now there's a child on the way," he adds.
He plans to tell his son what happened to his grandparents, but shares the reality: "Linda will be his gran."
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But their parents would be so happy to see their sons living full lives, Louis says.
He adds, "Knowing that we are still here and together, more importantly, would be some comfort."