I have a brother who has left Islam. I have trouble even looking at him now. Must we keep good relations with family members who have since left the faith?

Keep relations with him, but at the same time do not condone what he is doing.

The late Ayatollah Dastaghayb Shirazi wrote in his book Greater Sins: “If Sileh Rahmi towards a Kafir (disbelieving) relative, in some way, strengthens his conviction towards his own religious views; or if Sileh-Rahem towards a sinful relative provides him with opportunity and encouragement in his unlawful ways, then this kind of Sileh Rahmi is forbidden.

In fact, if Qat-e-Rahem induces a disbeliever to introspect and reconsider his disbelief, then, Qat-e-Rahmi is obligatory on us. In the same way Qat-e-Rahem is obligatory if it discourages or dissuades a relative in his sinful ways.”