Joint-heirs with Christ (sunklēronomoi Christou). A late rare double compound, in Philo, an Ephesian inscription of the imperial period (Deissmann, Light from the Ancient East, p. 92), papyri of the Byzantine period. See note on Rom 8:29 for this idea expanded. Paul is fond of compounds of sun, three in this verse (sunklēronomoi, sunpaschōmen, sundoxasthōmen). The last (first aorist passive subjunctive of sundoxazō with hina (purpose), late and rare, here only in N.T.