P.S : Not everyone will appear that frequently, but this is the list of occupants of the houses and their ages :
Characters age (y.o : year old)
Steamies House (41 people)
Jimena Greysworth (13 y.o(?))
Toad (13 y.o)
Kevin (13 y.o)
Bill (14 y.o)
Ben (14 y.o)
Thomas (15 y.o)
Percy (15 y.o)
Rosie (15 y.o)
James (16 y.o)
Emily (16 y.o)
Charlie (16 y.o)
Millie (16 y.o)
Luke (16 y.o)
Timothy (17 y.o)
Stanley (17 y.o)
Ryan (18 y.o)
Scruff (21 y.o)
Whiff (22 y.o)
Duncan (33 y.o)
Oliver (34 y.o)
Gordon (34 y.o)
Donald (35 y.o)
Douglas (35 y.o)
Henry (35 y.o)
Peter Sam (35 y.o)
Sir Handel (37 y.o)
Mike (37 y.o)
Marion (37 y.o)
Victor (38 y.o)
Duck (Montague) (38 y.o)
Porter (38 y.o)
Toby (40 y.o)
Henrietta (41 y.o)
Edward (42 y.o)
Rex (45 y.o)
Bert (47 y.o)
Rheneas (48 y.o)
Skarloey (49 y.o)
Glynn (53 y.o)
Stephen (55 y.o)
Duke (57 y.o)
Diesels House (14 people)
Philip (16 y.o)
Diesel (17 y.o)
Paxton (18 y.o)
Sidney (19 y.o)
Daisy (23 y.o)
Den (29 y.o)
Dart (29 y.o)
Iron' Arry (30 y.o)
Iron' Bert (30 y.o)
Norman (31 y.o)
Diesel-10 (32 y.o)
Rusty (36 y.o)
Mavis (36 y.o)
Salty (41 y.o)
Chuggington House (35 people)
Piper (4 y.o)
Hoot (13 y.o)
Toot (13 y.o)
Wilson (15 y.o)
Koko (15 y.o)
Brewster (15 y.o)
Tai (17 y.o)
Zephie (18 y.o)
Hodge (19 y.o)
Emery (19 y.o)
Payce (19 y.o)
Rosa (19 y.o)
Daley (22 y.o)
Cormac (23 y.o)
Tyne (25 y.o)
Fletcher "Fletch" (25 y.o)
Asher (28 y.o)
Harrison (34 y.o)
Chatsworth (34 y.o)
Skylar (35 y.o)
Hamish (35 y.o)
Harry (35 y.o)
Russ (37 y.o)
Hanzo (37 y.o)
Decka (38 y.o)
Jackman (39 y.o)
Zack (39 y.o)
Calley (39 y.o)
Irving (42 y.o)
Dunbar (43 y.o)
Skipper Stu (43 y.o)
Mtambo (45 y.o)
Olwin (50 y.o)
Speedy McAllister (55 y.o)
Old Puffer Pete (60 y.o)