I would say that anybody that knows who is in the backstreet or N'Sync from a picture is working on there Gayness.
Anybody who had a daughter between the ages of 8-18 in the mid 80s knew the names of the members of New Kids. Might only be able to recall one song (if that), but knew the names then and could probably remember at least two of them today.
Anybody who had a daughter between the ages of 8 - 18 in the early 90s knows the members of Backstreet and N'Sync. May not be able to correctly identify which songs go with which band but you know the names.
Anyone with a daughter between the age of 8-18 today knows the members of One Direction. May not know for sure which is which, not really sure which songs are theirs when they come on the radio, but you know the names. Zayn, Naill, Harry, Louis and Liam. Easy.
No different than knowing the names of the Beatles, Monkees or any other boy band that came before.