Is Mega a construx Lego?

Currently, Mega Construx is Mega Brands’ Lego-competing building brick sets. And, they later rebranded those sets as Mega Construx. So, Legos and the Mega Brand currently both have a brand for smaller blocks (Mega Construx and Lego) and a brand for larger blocks (Mega Bloks and Duplo).

What happened to construx?

Construx was discontinued in 1988, briefly revived by Mattel in 1997, and then discontinued again. Mattel resurrected the Construx name as Mega Construx in 2017 (see Mega Bloks). For a short time near the end of the Fisher Price run, a version targeted at younger children was released called Basix Construx.