Get related objects or related list object

You can get related objects with function :

public static map<string,string> getRelatedObjects(string masterObjectName){
map<string,string> relatedObjectsMap = new map<string,string>();
list<Schema.Childrelationship> relatedObjectsList = Schema.getGlobalDescribe().get(masterObjectName).getdescribe().getChildRelationships();

for (Schema.Childrelationship  relatedObject : relatedObjectsList) {
if(relatedObject.getChildSObject().getDescribe().isUpdateable()
&&
relatedObject.getChildSObject().getDescribe().getKeyPrefix()!=null
&&
!relatedObject.getChildSObject().getDescribe().isCustomSetting()
&&
relatedObject.getChildSObject().getDescribe().isCreateable()
)
relatedObjectsMap.put(relatedObject.getChildSObject().getDescribe().getName(),relatedObject.getChildSObject().getDescribe().getLabel());
   }
return relatedObjectsMap;
}