There are at least two religious orders that go by the informal name Christian Brothers. Both are Catholic lay orders dedicated to education. Despite rather strong similarities, the two orders are not related.
The Congregation of Christian Brothers is a Catholic lay order founded at Waterford, Ireland in 1802 by Saint Edmund Rice. It is dedicated to education, especially to the education of the poor. It also engages in ministry to the disabled.
The Brothers of the Christian Schools are a Catholic lay religious order founded in France by Saint John Baptist de La Salle in the period from 1679 to 1719. They are commonly called the Christian Brothers or the Lasallian Brothers. The order is dedicated to Christian education, especially to the education of the poor.