Seven
Roberto had one siter and seven brothers
He had 7 brothers and sisters. With him is eight kids.
He had 11 brothers and sisters.
2
There are three brothers and two 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.
One sister, two brothers
he had no brothers or sisters
Athena had no brothers or sisters.
2 brothers and sisters
One brother, two sisters ( if you're the second brother)
This is a logic puzzle. YOU are part of the puzzle, so you have equal brothers and sisters. Your brothers have twice as many sisters (meaning you) as they have brothers. So if you have one brother and one sister, they are equal. But if your brother has two sisters, he has twice as many sisters as brothers, right? It doesn't say that he HAS brothers, just that he has twice as many sisters as brothers. So you have a brother and a sister, but your brother has two sisters. Three kids, two girls and one boy.