Tomlinson, now an X Factor judge, lost his mother Johannah Deakin, 43, in December 2016 to leukaemia.
According to The Sun, Two Of Us contains lyrics about losing a loved one, with Tomlinson singing: “You’ll never know how much I miss you, the day that they took you, I wish it was me instead.”
Two Of Us is expected to be a single from Tomlinson’s upcoming debut solo album.
The song will be released on March 7.
Tomlinson found fame as part of boy band One Direction, alongside Niall Horan, Liam Payne, Harry Styles and Zayn Malik.
The group went on hiatus in January 2016.
Louis Tomlinson shares teaser of new song reportedly about late mother