Mother's Milk

Mother's Milk was the only member of the Boys and to be born with Compound V in his blood. His mentally retarded brother also developed superpowers, expanding his bodily mass. However, he died moments after his powers manifested as his body and head continued expanding in size while he wearing a helmet, crushing his skull. Mother's Milk's father then pursued legal action against Vought American, but died after winning one court case.
After his father's death, he joined the military and became a heavyweight champion. During his championship, Mother's Milk discovered the powers afforded to him thanks to the Compound V — these included superhuman strength, agility, stamina and durability. Not long after accidentally using these powers to kill someone, he was approached by Billy Butcher and joined the Boys.