Of *course* a person involved with a couple will usually feel a stronger connection with one member than the other. I mean, what two friends do you have that you felt exactly the same way about from the beginning? What two loves in your life developed in exactly the same way at exactly the same time? It *can* work out such that things are roughly equal, and I do believe that sometimes a person can feel NRE for a couple as much as for the individuals within it, but I think this is the exception rather than the rule.
Trying to force it is a very bad idea, feeling pressured tends to push people apart rather than bring them closer. Let it be what it is. If you have a strong connection with one partner and not the other, maybe what you have is a vee and not a triad. And that's ok. I honestly feel like the third/secondary/person-coming-in-from-the-outside had some responsibility but in the end it HAS to be up to the members of the preexisting couple to make sure that neither of them is feeling slighted or like a third wheel or whatever by the new relationship. If the natural shape of your relationship is more like a vee than a triad, or if it's not an equilateral triad, then maybe you should do more separate dates as twosomes and just hang together more casually as friends when it's all three of you rather than feeling like all three partners have to be together all the time with one of them just feeling unnecessary.
Forget what your friends think. Just tell them "Yes, we each have different relationships that look different because we're different people, that doesn't mean we don't all care about each other."
Getting together with my gf and her husband was a huge learning experience. Going into things, I had the misconception that it would make more sense for me to be dating both of them if I was going to be dating one of them. That would have been a huge mistake, because Eric wasn't ready to engage emotionally with me the way Gia was. Expecting each relationship to work the same way would have resulted in unhappiness all around.
Me, 30ish bi female, been doing solo poly for roughly 5 years. Gia, Clay, and Pike, my partners. Davis, ex/friend/"it's complicated." Eric, Gia's husband. Bee, Gia and Eric's toddler.