The answer will depend on which Edgar the question is about. I believe there have been more than one Edgars in the history of humankind!
Also, the correct spelling for the word, in this context, is "their".
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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
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.
7 brothers and sisters
He had two or three brothers and no sisters