The titular characters of Drake & Josh are stepbrothers with opposing personalities. The first episode is about their parents' wedding announcement, and ends with the two eventually accepting each other as brothers. Throughout the rest of the show, they're united in their dislike of Drake's little sister Megan.
Stranger Things: Billy and Max are new stepsiblings through the marriage of Billy's father to Max's mother, but it's explicitly an unhealthy and unhappy dynamic. Not only are things strained from their move to a small town in Indiana, but Billy is controlling and verbally abusive to Max because his father is physically abusive, while Max's mother doesn't intervene. And that's before the Big Bad takes advantage of Billy's vulnerability.