Can I have one of those

I'm stuck on a character in my latest story.   The best friend, a supporting role so to speak.
He's like the warm cup of tea on the cold afternoon instead of the shot of bourbon, the sweet scent of apples and cinnamon instead of the sharp tack of mint and lemon.
He's there, just to the left of my mind, waiting, wanting my attention.

Now, if I could just figure him out in the plot of the story as well as I just wrote that paragraph I'd be golden.
And I've tried writing the piece without him, but it doesn't feel right.  I know what he looks like, I know what he sounds like when I close my eyes, can imagine him down to the length of his sideburns. But I can't seem to settle on what to have him do in the story.

Why is he there?  Other then to be the balance to the lead character?  Sometimes it's the supporting characters that are hardest to write. The ones that need the most attention.
The backbone of the story.