I think I have a better understanding of your situation now, thank you.
But another possibility for them growing their relationship is to actually spend less time together. "Absense makes the heart grow fonder" and all that...
Is there really a "way to be" with a woman as a woman that's intrinsically different than the "way to be" with a woman as a man? I've always just been "who I am" when in a relationship, and gone with the flow. If she takes some cues on how to be with Nikki by seeing how you are with Nikki, and vice-versa (Nikki seeing how you are with Wifey), then you'll all learn things about each other that you might not learn if you try to keep the distance.
But I'm no expert, and if what you're doing is working for your family, then that's what really matters. I just always feel that if something's not working for me, I don't just "do it harder" but I try to do something completely different...
“As I am sure any cat owner will be able to tell you,
someone else putting you in a box is entirely different
from getting into a box yourself.” —bisexualbaker