Answer:
17
Step-by-step explanation:
Cronus had 17 siblings: Oceanus, Hyperion, Coeus, Crius, Iapetus, Mnemosyne, Tethys, Theia, Phoebe, Themis, Rhea, Hecatoncheires, Cyclopes, Giants, Erinnyes, Meliads and Aphrodite. So the answer to your question would be 17.
Hoped that helped! ;P