foster brother
/ˈfɔːstər ˈbrʌðər/
noun
- A male child who is raised in the same foster family as another child, but is not biologically related to that child.
- Even though they were foster-brothers, they had very different personalities.
- My foster-brother and I shared a room for five years and became as close as real siblings.
- He introduced his foster-brother to his friends at the family reunion.