When I reread it again, there's part when Emiel said how old he was when he started working as a knight...? and If I'm not wrong, they said it was 5 years ago.
Not long after that part... I think? It was said that Estelle is 11, so maybe their age gap is around 6-8 years.
kinda want a slyvie plushie. she's just so so sooo cuteeee