These believers, many of whom have gone on to their final reward, are part of the Oriental Orthodox stream of Christianity, which the
rest of the church excommunicated in 451. They remain in schism from the Eastern Orthodox church today, and their theological viewpoints would also be in conflict with orthodox evangelical Christianity, as evangelical Christianity's theological viewpoints on issues like christology and the Trinity are aligned with, and originated in, Roman Catholicism.
Yet despite these differences, I would be glad to call a member of such a congregation a brother, as I did the last time I ran into a Coptic person who walked up to talk to us when I was with a group doing street meetings. He thanked us for our work to sing on the streets and to pass out tracts, and I thanked him for coming over and talking to me.
I think it's worth noting that
Pope Francis is going to visit Egypt for two days in solidarity with Coptic Christians who are being targeted. I'm glad he is choosing to put theological purism behind him and focus on things that look a lot more like how Jesus taught us to treat each other.