The 23-year-old has decided to change his last name, his grandmother, Vanessa Redgrave, told the Daily Mail in an article published on Saturday.
"He’s taken, officially, the name of his mother. He’s Micheál Richardson, not Micheál Neeson," the 81-year-old actress revealed. "That wasn’t because he wanted to avoid his father’s fame, which is enormous. He wanted to hold his mother close to him, because she was a remarkable actress. Absolutely remarkable."
Micheál was only 13 when his mother died in 2009 after hitting her head in a skiing accident. Neeson and Richardson married in 1994 and shared two sons together: Micheál and Daniel, 22.
"[Her death] was never real. It still kind of isn't," the actor expressed. "There's periods now in our New York residence when I hear the door opening -- especially the first couple of years -- anytime I hear that door opening, I still think I'm going to hear her."
"It hits you. It's like a wave," he added of dealing with his grief. "You just get this profound feeling of instability... the Earth isn't stable anymore, and then it passes and it becomes more infrequent, but I still get it sometimes."
The actor also admitted that he began drinking too much after Richardson died, but quit in 2013.
"I was just -- I was drinking too much. It started since my wife died," Liam told GQ in March 2014. "Pinot Noir: That's all I drink. I was never into spirits or liquor, hard liquor. And I gave up the Guinness years ago, because it just past an age, it sticks to you, you know? So last year, I just thought -- they've been throwing these action movies at me, and I thought, 'Okay, let's just change it a little bit.' And it's been great. I love it."