TECHNICALLY IT'S POSSIBLE FOR HASHIRA TIMELINE TO LOOK LIKE THIS BECAUSE OF LOSE TIMELINE:
•The stone piller Gyomei became a hashira at age 19 and was 27 to 28 years old in current events (9-8 years)
•The sound piller Tengen became a hashira at age 18 and was 23 in current events (5 years)
•The water piller Giyuu became a hashira at age 14-15 and was 21 in current events (6-7 years)
•The flower piller Kanae became a hashira at age 16ish and died at age 17 (1-2 years)
•The wind piller Sanemi became a hashira at age 18 and was 21 in current events (3 years)
•The insect piller Shinobu became a hashira at age 16 and was 18 in current events (2 years)
•The flame piller Kyojuro became a hashira at age 18ish and was 20 in current events (2.5 years)
•The serpent piller Iguro became a hashira at age 18 and was 21 in current events (2 years)
•The mist piller Muichiro became a hashira at age 12 and was 14 in current events (2 years)
•The love piller Mitsuri became a hashira at age 18 and was 19-20ish in current events (1.5ish years)
Which means the Hashira line up could've looked like THIS at some point:
1.) A GIANT, blind Buddhist monk with a mace chained to a cleaver who is built like a brick shit house
2.) a thunder breathing master with a short temper
3.) canonically one of the MOST TERRIFYING MOTHERFUCKERS who's about to quit due to the death of his wife
4.) a depressed 15 year old with too many issues