When I write each storyline, I treat the character being focused on as if they're Connor's co-lead to make sure they get the attention they deserve. Their storylines all differ, so some will weave into the game at different times and in different ways, but I do think I pay the same amount of attention to each of the romance guys.
That's one of the reasons the upcoming update has taken so long. All the storylines converge at one point, and since they can vary so much based on choices, it involves a lot of writing and some complicated coding. But I think it's been worth the effort for the reactivity.