Sis
short brother
siblings means brothers and sisters. It appears the application form is inquiring about how many siblings (brothers and sisters) you have.
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.
Athena had no brothers or sisters.
he had no brothers or sisters
brothers and sisters
no she has no brothers or sisters.
Black beard had no sisters or brothers
2 brothers and sisters
She had 12 brothers and sisters
yes, 7 brothers and sisters