I don't know about your brother but his take on yoga is correct.
The word yoga means "union," and the goal is to unite one's transitory (temporary) self with the infinite Brahman, the Hindu concept of "God." This god is not a literal being, but is an impersonal spiritual substance that is one with nature and the cosmos. This view is called "pantheism," the belief that everything is God and that reality consists only of the universe and nature. Because everything is God, the yoga philosophy makes no distinction between man and God.
Hatha yoga is the aspect of yoga that focuses on the physical body through special postures, breathing exercises, and concentration or meditation. It is a means to prepare the body for the spiritual exercises, with fewer obstacles, in order to achieve enlightenment. The practice of yoga is based on the belief that man and God are one. It is little more than self-worship disguised as high-level spirituality.
More at this link.
https://www.gotquestions.org/Christian-yoga.html
Since there is nothing new under the sun, I have heard some say, that Mormonism is loosely based this philosophy, that man and God are one, because they make the blasphemous claim that man become a god.