The people on the Usenet newsgroup alt.culture.us.1980s, back when I used to read it, had two definitions of this phrase, which caused some conflict between readers. Some felt that to be a child of the 80s you had to have been born during the decade and were a kid during it. The opposing group said that you had to be old enough at the beginning of the decade to have been influenced by the pop culture and events that happened during the 1980s; in other words, you were probably a teenager during the 80s. Neither side really won out while I was there.