
I know his age, that still doesn't change the fact the curse did stunt his growth
http://www.mangago.zone/read-manga/sincerely_i_became_a_duke_s_maid/ml/mpn_chapter-2145432/pg-4/
kids don't grow that much in days, it tends to be gradual.
http://www.mangago.zone/read-manga/sincerely_i_became_a_duke_s_maid/ml/mpn_chapter-2148974/pg-3/
So both of us are correct (๑•ㅂ•)و✧

It's normal for a girl to look exactly the same since she was 17-21 (by the way it's been only 4 years not 10+ years).. Alejandro used to look like a child because of the curse, he was 13 when ibelina first met him but he looked 8-9 because his body didn't grow up properly (because of the curse), that's why when he suddenly grew up fast after he's cured
Alejandro got hit by a truck called puberty while Ibee be looking the same for more than 10+ years. What is with that?