I have Created two Objects say Teacher__c(Parent) and Student__c(Child) having similar fields such as name, email, mobile and Address. and they have two unique fields on both objects such as teacherid__c on teacher object and id__c on student object On deleting record of Teacher__c, associated Student__c record should be deleted and vice versa.
here in my code insertion and updation is working but deletion is not working can anyone help me doing that
code:
trigger TeacherTrigger on Teacher__c (after insert, after update, before delete) {
    if (Trigger.isAfter) {
        if (Trigger.isInsert) {
            List<Student__c> studentsToInsert = new List<Student__c>();
            for (Teacher__c teacher : Trigger.new) {
                if(triggerCount.runonce()){
                    Student__c student = new Student__c();
                    student.Name = teacher.Name;
                    student.Email__c = teacher.Email__c;
                    student.Mobile__c = teacher.Mobile__c;
                    student.Address__c = teacher.Address__c;
                    student.id__c = teacher.Id;
                    studentsToInsert.add(student);
                }
            }
            if (!studentsToInsert.isEmpty()) {
                insert studentsToInsert;
            }
        }
        if (Trigger.isUpdate) {
            List<Student__c> studentsToUpdate = new List<Student__c>();
            for (Teacher__c teacher : Trigger.new) {
                if(triggerCount.runonce()){
                    List<Student__c> existingStudents = [SELECT Id, Name, Email__c, Mobile__c, Address__c, id__c FROM Student__c WHERE id__c = :teacher.Id LIMIT 1];
                    if (!existingStudents.isEmpty()) {
                        Student__c student = existingStudents[0];
                        student.Name = teacher.Name;
                        student.Email__c = teacher.Email__c;
                        student.Mobile__c = teacher.Mobile__c;
                        student.Address__c = teacher.Address__c;
                        studentsToUpdate.add(student);
                    }
                }
            }
            if (!studentsToUpdate.isEmpty()) {
                update studentsToUpdate;
            }
        }
        if (Trigger.isDelete) {
            list<String> teacherIds=new list<String>();
            for(Teacher__c teacher:trigger.old)
            {
                teacherIds.add(teacher.id);
            }
            list<Student__c> listOfStudents=[select id,id__c from Student__c where id__c in:teacherIds];
            System.debug('Number of students found: ' + listOfStudents.size());
            system.debug('listOfstudents'+listOfStudents);
            if (!listOfStudents.isEmpty()) {
                delete listOfStudents;
            }
        }
    }
}


trigger StudentTrigger on Student__c (after insert, after update, before delete) {
    if (Trigger.isAfter) {
        if (Trigger.isInsert) {
            List<Teacher__c> teachersToInsert = new List<Teacher__c>();
            
            for (Student__c student : Trigger.new) {
                if(triggerCount.runonce()){
                    Teacher__c teacher = new Teacher__c();
                    teacher.Name = student.Name;
                    teacher.Email__c = student.Email__c;
                    teacher.Mobile__c = student.Mobile__c;
                    teacher.Address__c = student.Address__c;
                    teacher.teacherid__c = student.Id;
                    teachersToInsert.add(teacher);
                }
            }
            
            if (!teachersToInsert.isEmpty()) {
                insert teachersToInsert;
            }
        }
        
        if (Trigger.isUpdate) {
            List<Teacher__c> teachersToUpdate = new List<Teacher__c>();
            for (Student__c student : Trigger.new) {
                if(triggerCount.runonce()){
                    List<Teacher__c> existingTeachers = [SELECT Id, Name, Email__c, Mobile__c, Address__c, teacherid__c FROM Teacher__c WHERE teacherid__c = :student.id LIMIT 1];
                    if (!existingTeachers.isEmpty()) {
                        Teacher__c teacher = existingTeachers[0];
                        teacher.Name = student.Name;
                        teacher.Email__c = student.Email__c;
                        teacher.Mobile__c = student.Mobile__c;
                        teacher.Address__c = student.Address__c;
                        teachersToUpdate.add(teacher);
                    }
                }
            }
            
            if (!teachersToUpdate.isEmpty()) {
                update teachersToUpdate;
            }
        }
        if (Trigger.isDelete) {
            list<String> studentIds=new list<String>();
            for(Student__c student:trigger.old)
            {
                studentIds.add(student.id);
            }
            list<Teacher__c> listOfTeachers=[select id,teacherid__c from Teacher__c where teacherid__c in:studentIds];
            system.debug('listOfTeachers'+listOfTeachers);
            if (!listOfTeachers.isEmpty()) {
                delete listOfTeachers;
            }
        }
    }
}
Thanks