Alright, so this is going to he a tough one to answer because of the reasons outlined here and here. It’s just not a ship I have much inspiration for however I will try to give some headcanons.

• They first bond over her ancestor Emily. Though he didn’t pay much attention to Emily then, having been involved with Katherine, he still remembers her fondly. He recalls his time with her for Bonnie’s benefit who is in desperate need of connection to the Bennetts.
• They study together. Stefan isn’t in much need having been over a century old but he comes over for Bonnie who is in danger of flunking with all she’s been doing for the MFG.
• Their friendship starts when he checks in her after the car wash incident. Feelings eventually grow from friendship to romantic but it takes time for both of them to act on it. First there was the Elena factor, then there was Damon, but what really kept them apart was not wanting to ruin what they already had.
• When they do get together they’re pleasantly surprised when things don’t change much between them. They still have movie nights, they still hang out with their friends, the only thing that’s changed is when they want to jump each others bones they can.
• When Stefan is going through a weak moment Bonnie is there to put him in his place. She won’t be with a murderer so she reminds him everytime that he might lose her.
• Ripper Stefan is all about Bonnie. She tries not to give in, she doesn’t want to enable him, but she hates to admit how much hotter he is.
• They easily settle into a pattern but often roleplay in and out of the bedroom..it sometimes gets so crazy that they forget the sex and just have fun pretending to be other people.

And that’s all I have sorry if you were looking for more or something different.