Subject Rename a foreign key
Author Рустам Муса-Ахунов
Use "ALTER TABLE ... DROP CONSTRAINT ..." and then "ALTER TABLE ... ADD CONSTRAINT ... FOREIGN KEY ..."

Where you see such FK name as "RDB$FOREIGN60"? It created by you or some DB management tool? As I know, there is no automatically generated ("system") FK's. So, you must create them manually and assign meaningful name to it.