Is the questioner entitled to file a lawsuit against his paternal uncle, who seized his siblings’ inheritance and built a mosque with it without their knowledge, and refused to divide the inheritance, given that the questioner knows his father refuses to sue his brother?

What your uncle did—if things are as you mentioned—is a major sin and an unlawful aggression. Those who have the right to file a lawsuit against him are the heirs who were deprived of their inheritance. If they choose not to file it, no one else can do so. If they die and their right to inheritance passes to their heirs, then any of their heirs may file this lawsuit.