Our elderly father wants to take another wife. Can we children voice our objection in the process?

Children are not parties to the application, but you may express your concerns to your father respectfully and support your mother in her rights. The court calls the existing wife to be heard; your mother is the main voice there. Your role is to help your mother understand her rights and to accompany her if she wishes. To your father, convey your concerns respectfully, for example about his health, your mother's maintenance and his ability to look after two homes. Allah says: “And, out of kindness, lower to them the wing of humility” (Surah al-Isra' 17:24). Avoid boycotting your father or cutting ties. If the conversation reaches a dead end, ask a respected elder to mediate. See an older man wanting polygyny.