And when you are responsible for writing a game that is pretty much fanservice to fans of the characters, it is incredibly important not to misrepresent the character.
If you are getting paid to do this, try to do more than just scan the web and pick up fan jokes of characters. Yes, fans make fun of how Cecilia (Fuuin no Ken) looks old. But if I recall correctly, her official setting is NOT OLD. So stop making her talk about her age! It's like being forced to read a bad doujin, except it's not fan-based but official.
Oh, and BTW, his Japanese voice sucks too. But it actually fits THIS FAKE EPHRAIM, so in a way, it makes sense that his voice sucks. Because the representation is faulty from the start!
And BTW again, but as you can tell from Wada Sachiko's Tweeter, you can tell the original artist for the game clearly isn't happy either, even though she says it way more subtly than me.
Let me be blunt. THIS IS NOT EPHRAIM!
He is not the character that openly talks about sibling love. In fact, you can say he doesn't even realize how close he is with his sister. He's more of the type that usually teases his sister (which he does in the game), but in the end, they are close to each other at heart.
In fact, Erika is the one that is more of the "Please spend time with me, Onii-chan!" type, even though that is an exaggeration too.
Oh, and guess what? Ephraim is the type of person willing to charge into a fortress with only 4 people, even while those people are trying to tell him it is crazy to try it. But he charges in and does what he needs to do.
In fact, this line more resembles that boss who you fight in Chapter 14 or something, the one surrounded by mountains where the merchant later pops up on the left. Why is Ephraim saying this? Because the writer couldn't find a more natural way to extend the storyline (for what worth the story even has)?
EDIT: Oh, and to be clearer, Ephraim does say this line in the game too. Except the way he uses it is the exact opposite and very cool. One of the reasons he is liked.
Another proof the writer did not bother to study the original source. Using a line from the game sounds smart, right? NOT WHEN YOU DON'T KNOW THE CONTEXT OF IT!