Poll Results

Total votes: 2979

None: 349 (11.7%)
One: 1242 (41.7%)
Two: 817 (27.4%)
Three: 320 (10.7%)
Four: 105 (3.5%)
Five: 70 (2.3%)
Six: 28 (0.9%)
Seven: 15 (0.5%)
Eight: 6 (0.2%)
Nine: 3 (0.1%)
Ten+: 24 (0.8%)

I deliberately didn't address the questions of half-siblings, adopted siblings, deceased siblings, and siblings-in-law, leaving it up to you to decide for yourself how to account for those.