Are people born in 1989 and 1996 the same generation?

My cousin that was born in 1989 keeps saying the 90s were the bom when she wasn’t even old enough to remember the WHOLE 90s. Real 90s kids remember the whole decade. Her sister said, “We’re only six years apart and plus there’s stuff you and I remember like high school music and Avril Lavigne.”
She said yeah but she may not remember late 90s or earlier 90s shows or movies.
She was born in December 1989 and her sister was born on January 1996.

Are people born in 1989 and 1996 the same generation?
Post Opinion