The first thing you have to ask yourself if you want these relationships to come to life is, "How does this character view my MC?" Let's check out an example!
Let's go with Harry Potter on this one, shall we? There are too many characters to mention so we'll look at just a few key people. (See what I did there? They're so real they're people)
- Ron: Harry's BFF, he loves the guy and would lay down his life, but he also has some jealousy issues. He's constantly overshadowed by Harry after all, just like he was by his siblings growing up.
- Snape: Wow. The whole complex mystery behind this character truly revolved around just this question, didn't it? Harry represented everything he wanted but couldn't have, meaning (spoiler alert) Lily Evans. And to make it worse, the woman he loved chose the man he despised most, his tormentor in school, who Harry happens to be the spitting image of. Except for those eyes. Lily's eyes must be a constant reminder to Snape of the mistake he made and the promise he lives to fulfill. Talk about complex and mixed feelings.
- Mrs. Weasley: The mother Harry deserves. And indeed, she loves him as a son, to the point that she attempts to protect him when it's nearly impossible. She is his surrogate mother.
- Petunia: Lily's sister and Harry's aunt. Harry is a constant reminder of everything she wanted but was denied. Another case of jealousy, which is why Harry is treated so horribly by her entire family.
Do you see what I'm doing here? It's like looking at motivation, but it has to be directly related to the MC. This defines the dialogue and the general interaction/choices that the characters make in relation to the MC and therefore the plot.
One more example that we'll make up. Say we have a love triangle. Ouch! Pointy edges. The MC is a girl named... Julie. Her two boys are Sean, who has loved her from across the street for years, but scarred by his childhood he uses sarcasm to disguise his true feelings, and Carl, the hottest guy at school who sees her as his best arm candy. Now of course she doesn't know this, nor do we the readers at first.
Great, just what I need right now, Sean. I try to concentrate on my broken heel instead of the dark eyes that always penetrate my defenses. He's probably coming to gloat.
"You have a run in with a yetti at that dance?" He smirks and I resist the desire to smack him or burst into tears.
"Yeah, that's exactly what happened. Why don't you go back to brooding in your room?"
His grin turns into a scowl. "Are you okay? Did he hurt you?"
"Why? You want to give him a high five?"
Okay, now one with Carl:
"Nice performance in Lit."
I glance up from my Tuesday Special to find Carl Landers standing over me in all his ripped glory. Is he teasing me? No, his eyes crinkle in the corners and his smile... Oh wow. Don't drool, Julie.
"Thanks," is all I can muster.
He straddles the bench next to me. "I have a game this weekend."
As if a single person in this lunchroom wasn't aware of that.
"Are you going?"
I take a sip of water to wet my dry mouth. "I don't know. I hadn't thought about it much."
"The school needs you there," he says.
I narrow my eyes. "How do you figure?"
"Well, if you're there, in the front row, I'll play better and maybe we'll win Homecoming."
Now go write out your characters viewpoint of the MC and try writing a few practice scenes.