When describing the abuse they went through, some genital trauma is described (they go into surface details, but I suspect the description could still be triggering for some). I'm not through the entire series yet, but I'd say most of this is in episode 5.
The show explores multiple possibilities and perspectives (the kid’s version of events, versus the parent’s, versus the outsider’s) and sometimes these conflict with each other.
One of the brothers sexually abused the other when they were both children. The abused brother forgives him because they were both abused by their father, and he was reenacting what had happened to him.
As a child, the older brother was abused by their father and then reenacts the abuse he experienced on his little brother. Discussed, not shown. Also it’s implied that the abusive father was himself abused as a child. So, big yes.
Child abuse is a major part of the story/case so it is discussed frequently and is pretty much unavoidable if you’re watching the series. You will see teenage boys being verbally and physically abused by their parents. You will hear graphic accounts of them being abused as children.
Cocaine is used in an early episode. In later episodes with flashbacks/backstory (Particularly episode 6), a woman is shown struggling with addiction to pills and has an episode where she collapses (apparently from an overdose). She also describes a past overdose in this episode.
Graphic descriptions of child sexual assault throughout, but particularly Episide 5, the entire episode is one of the brothers describing in detail how their parents abused them sexually, physically, and emotionally.
F word used several times. The timeframe for a lot of the events is also at the peak of late 80s and early 90s homophobia following the AIDS epidemic, so there’s a lot of casually homophobia rhetoric throughout.