I am with Gimlet. It isn't your job to be a parent to this kid! It's 100% on the actual parents. You have already gone above and beyond.

Relationships should develop naturally, if SS isn't interested, so be it. If you aren't interested anymore- Oh well! Not your kid! 

"SM needs to TRY HARDER"  (TM)  Patent Pending.  

GAG!  Failing disengagement,  "throw this one back" as is the popular expression.

How can you possibly love or respect this man anymore? He allowed his kid to fail a grade three times? His son will never leave home. Throw this rotten fish back in the sea for the sharks to devour and cast your line out for a shiny, handsome fish with no parasites.

The brother is an idiot. What good does he think that will do? 

As for them being Mediterranean, they clearly pick and choose what they've "inherited". If any Mediterranean disrespected their grandmother or aunt the way your SS does, he would be made to be sorry ASAP! You do not disrespect your elders! 

You are in for a long dreary time of it if you follow the brothers advice.

Stop doing for the kid.

Really consider if this is the right relationship for you. 

His kid is a jerk. Do you really want to support him after 22 and he still hasnt graduated high school?

They dont change they get worse if the parents are failing their job as parents.

Is you have a BF who a lousy parent.  Allowing his DS to be failer.  He has no common sense.  Then you have a FSS who does not care about repeating 8th grade three times,  does not care what his school mates think of him. 
 

You should take a long hard look at this relationship,  there has to be other future issues.  

"Try harder" makes me crazy. My ex came from an Italian family (but he's second generation born in the US). He had an anger issue and frequently told me "that's just the way he is" because he's a fiery Italian. And I had to learn to deal with it. (Apparently Italian men can't control themselves?) Well, eff that. His anger frightened me and that's just the way I was, so why didn't HE have to accept that? No, I was the one who had to try harder. Notice he is now my ex.

Go for cordial. That's it. Leave the parenting to his dad.

Thank GOD he is only a boyfriend.

Miss,  pack up your stuff and run...fast. Far from this guy.

Oh, and do not look back either.

Be safe, ok?

I've cleaned his room multiple times, done his dishes, laundry, offered to help him with homework, and paid for his birthday presents and given him treats and junk food that he likes numerous times

The only thing that you need to try harder at, is disengaging.

Give him your heart? I don't think so.

When my SDs were in their mid teens, I got a message from NPD BM via DH that I needed to "make more of an effort" with them.  This despite the fact that NPD BM had spent 10 yrs PAS'ing them against me, so that I could have been Mother Teresa and they still would have hated me.  So I would take any message about "trying harder" with a very large pinch of salt. 

Now for a repeat 8th grade three or more times story.  

When I was in Jr. High School, what is called MIddle School these days, I was assaulted with a knife by an 18yo 9th grader.

This guy had been held back 3 or 4 times.  

Long story short, he tried to force me to step on the school crest on the floor of the Jr. High foyer. Which was a bit no no.  I refused, he attempted to drag me over the crest, unsuccessfully. So, he pulled a knife and backed me against the wall with the knife.  A Cheer Leader showed up at that point and he tucked the knife in his jacket.

My parents picked me up from school after track practice and we headed home for dinner.  They noticed blood on my shirt where he had nicked me with the knife.  When they asked, I told them what had happened.  They reported it to the school.

A few days later a police officer removed me from class and informed me that they would be in an office behind the student services counter and wanted me to  walk by the glass window between the foyer and the office area and if I saw the perpetrator to proceed past the window and inform the officer that would be waiting on the other side in the hallway. I nodded and two officers stepped out of the office behind the 18yo 9th grader and cuffed him. He had the knife in his jacket pocket. He disappeared never to seen again.

And.... another multiple time Jr. high failure in my neighborhood decided he wanted to kick my ass. I overheard him in my front yard talking with another kid about knocking on my door to get me outside at which point he would kick my ass. So, I stepped out of the front door and took a seat on my younger brothers kid sized Schwinn bicycle.  He moved aggressively toward me at which point I jumped up and smashed the bike on his head and proceeded to beat him bloody with the bike.  He was several years older than me.  My parents were not home at the time.

So, his father came over to complain about what I had done to his kid.  A couple weeks later the same event restarted. The kid was hiding behind  bushes outside my door when I overheard him and another kid plotting my demise.  So, I got my CO2 air pistol, filled it with BBs, added a fresh CO2 cartridge, went out the back door, walked around the house behind them and proceeded to fill his ass with BBs chasing him down the street.

A few weeks later he was arrested for raping his 6yo little sister.

That your BF and his idiot brother are Mediteranian and passionate people is complete horse shit.  This an ill parented, ill behaved failed family spawn and he and the father need a swift kick in the ass.  So does the Uncle.  This kid has no business being in 8th grade for a 3rd time.  The other kids should not be forced to suffer his presence. And neither should you.

smh

I have lived much of my life around and working with Mediteranians and Middle Easterners.  Don't ever think that their region of origin justifies this shit. It doesn't.  My younger brother was born in Beirut. You don't get more Mediteranian than Beirut.

Tolerate no crap from any of these jackasses.

Good luck.