brotherless
/ˈbrʌðərlɛs/Definitions
1. adjective
having no brothers; without brothers
“She was a brotherless child, raised by her loving parents and sister.”
2. adjective
not having a brother
“The young girl felt sympathy for her brotherless friend who had recently lost their brother in an accident.”
3. noun
a person or thing that has no brothers
“In a family with many children, there was only one brotherless member.”