Others have pointed out siblings, but it's also worth noting that, in the context of your comment, sisters and brothers is more correct. Sibling is more clinical and might be used in a description like "I have 3 siblings, 2 brothers and 1 sister". When you are addressing a group, the more familiar brothers and sisters is appropriate. "May the force be with you, siblings" would be very weird.
Others have pointed out siblings, but it's also worth noting that, in the context of your comment, sisters and brothers is more correct. Sibling is more clinical and might be used in a description like "I have 3 siblings, 2 brothers and 1 sister". When you are addressing a group, the more familiar brothers and sisters is appropriate. "May the force be with you, siblings" would be very weird.