Of all the Simpsons adult characters, Sideshow Bob seems to be the one who gets paired with the biggest amount of characters (not counting OC's, that's it). The more common ones are (in order): Bart, Cecil, Sideshow Mel, and (usually older) Lisa. My original idea was to draw a very annoyed Bob getting smothered by all of them, but then I decided to do something different: show how *I* think the relationships would work if they were all kept in-character. No romance, no sex, just friendship.
Bart: I can imagine Bart and Bob becoming friendly rivals, or at least Bob accepting Bart as a worthy opponent, but always in a distant sort of way. So, I drew them as how they appear in the cover for the comic "Angels with yellow faces", in which Bart *almost* becomes Bob's apprentice.
Lisa: I'm not sure about how Bob sees Lisa, but I guess he sees her as an equal, but, oddly enough, not as an enemy, despite having her foiling most of his plans. He probably sees her with a mix of admiration and envy (she's already smarter than him at age eight!). I already drew them playing chess, so here I drew them reading; Bob is reading "One-hundred years of solitude", while Lisa has "Don Quixote". Both are very important ( historical and culturally) novels of Spanish-speaking countries, and are obligatory for all Latin-American high-schoolers, though Don Quixote, despite being VERY long, it's lots of fun (at least to me), while "Solitude" is just weird and confusing (though certainly unique).
Cecil: I hate incest, period. So here we have a nice brotherly moment.
Mel: Despite their differences, Mel and Bob have many things in common: both are smart, cultured, waste their talents in bad jobs, and have been abused by a jerk clown. They could be good friends, they'd have a lot to talk about, though they could end up doing nothing but whine and complain about Krusty, but at least is something.
Soon I'll draw another one, featuring characters Bob has interacted with in the show, but never gets paired with, despite having potential (remember him dating Edna?).