On all paths, Emma begins to develop romantic feelings for the MC.Yeah, it can happen even when you think you're firmly "not on the Emma path". Happened in my playthrough and I'm on the "Charlotte's sister" path (can't remember the name or be arsed to look it up right now).
On Charlotte's path, these feelings do not deepen, as her desire for the MC to marry Charlotte and become her father takes precedence.
On Lucy's path, the situation is more complicated. Since the MC is not going to become her father, that conflict is absent. However, she does not want to interfere in her aunt's relationship with the MC. As a result, her feelings continue to grow, but she struggles with them.
On all other paths, Emma's feelings for the MC develop more strongly, leading to the possibility of you choosing her as your love interest.