Emiel is only 7 years older than estelle, right ? Don't tell me this age gap disgust you, or i will be mad, especially when i have friends with the same age gap or even 10y old.
The romance don't happen before the timeskip anyway, when she will be 16 or 17 y old, so you should not have problem with that, she will not be small anymore (because she didn't eat enough when she lived with her mother) 
 and will look like a pretty girl.