None, although in the (non-canon) cartoon "Sonic Underground", he had a brother named Manic the Hedgehog and a sister named Sonia the Hedgehog.
7 brothers and 1 sister brothers: shadow , silver , blue ,blade , scourge , manic sisters : sonia
Sonic has one sister named Amy and three brothers named Shaow and Silver. Report if one more edit. Sonic's sister and brother appear in Sonic Underground. His sister's name is Sonia and his brother's name is Manic.
He had 11 brothers and sisters.
There are 4 brothers and 3 sister's all up. Assume your one of the brothers - hence you have 3 brothers and 3 sisters. However any one of your sisters, would have 4 brothers and 2 sisters.
There are three brothers and two sisters.
One sister, two brothers
Shadow. My brother watches the show all the time
One brother, two sisters ( if you're the second brother)
he had no brothers or sisters
Athena had no brothers or sisters.
2 brothers and sisters
Sonic only has siblings in the non-canonical TV series Sonic Underground. He has a sister, Sonia and a brother, Manic.