Destroyed there [ in there minds ] a great life.   You know if BM and BF were living together m we would be a happy family. Going to Hawaii, visiting Disney 5 times a year . There would be money to but SK a shiny new car. Everything will be gum drops and chocolate.   You as the SP stop all of this joy for them.  
Everything  was so great that's why parents got a divorce.   

It sounds like your skids hrew up in a very toxic situation that started before you came along. PAS, as well as mental health issues in the one who committed suicide. You didn't break it so you can't fix it. You might get blamed for it, but the best you can do is not tolerate disrespect and live your best life. 

I said this similar thing in a past post 

These skids (who are being raised by their breeder and Disney bio parent) are petty and jealous for no real reason

In my past sitch, I dealt with a Disneyland dad whose conniving manipulative ex wife would had this "I don't want another woman around my kids" type attitude 

Like girl I don't want to be around your lazy loud obnoxious cash grabbing demanding kids either tbh (dude can visit those kids at YOUR house, the library, the park, or wherever)

But since the law forces parents to take custody or face consequences, the Disneyland dad tries to be a good dad, and the custody spot is always the home you share, then I had to deal with her kids in my space every mf-ing weekend and holiday. 
 

In my mind it's like how dumb and jealous do you have to be to be willfully obtuse about the fact that another adult in the household is going to bring extra resources you bumbling idiots  

Even when we disengage from disrespectful spawn skids we STILL bring extra resources resources that benefit those ingrates 

Hell when my bio had a step mom at first I was turned off but then i quickly realized that this woman is taking care of my kid, freeing up my time, and doing me and my bio a favor

When I met the lady in real life I thanked her

I can only blame the parents, a lot. If the kids are not encouraged to develop a relationship with the SP, and the bio parent doesn't accept the SP as a parent or true partner in raising the kids then the kids will never have a relationship with the SP. It's even worse if PAS is thrown in. And you have a passive bio-parent. I hit the jackpot in all of this. The skids were great at first but two years in an OSD hated me, YSD18 was ok until her mid-teen years. I think eventually I'll have a relationship with YSD but with OSD20 I can't see happening. The good think is my DH has been doing a lot of work on himself and has 100% acknowledged my poor relationship with his skids is his fault (I also though remind him BM most certainly also had a part in it).  He's working on repairing his relationship with YSD18 and I do think that will help with me and YSD too.

SD14 totally ignores me and BS3 unless one of us says something first. If we are sitting on the couch in the living room, she will take a detour, walk all the around through the dining room, just to get to the kitchen. It used to bother me, but now I find in sad and also funny a 14 y/o can be so petty. What a sad way to live and also does she think it hurts my feelings? I would rather her attitude and rudeness not be around my BS3, so I am totally fine with her ignoring me.

When they were a family with BM and BF. The kids feel thing we're going to change.  For the good until you cane along.  You broke up the birth parents getting back together and being a happy family.  [. Both birth parents giving there kids everything there little hearts want ].  YOU. and only YOU screwed up there life.  Causing BM to go nuts and go away with her BF.  Again and again. And again. 

Thats why you disengaging from all this BS is most important.  If they dont want  to say good morning or thank you.  Not important, because ..you will be doing nothing for them... so there no need to thank you.  And if they are in your home it's not a good morning.

At age 5, YSS was literally walking/running into me as though I didn't exist.  He was actually pretending not to see me and if he pretended hard enough I would go away

SS annoyed me a lot when he was a kid but he was expected to be respectful to me.  BM and my husband expected it.  BM understood that I was helping to raise him and I think she grew to appreciate me for it.  I had permission from both her and my husband to discipline him and they backed me up.  She did like to cause problems at times but not in a encouraging SS to be a disrespectful little brat.  It was mostly things to annoy us.  He treated me more respectfully than he did BM, SIL, and MIL.  That's because they allowed him to treat them however he wanted.  I didn't allow it.  He was never rude never ignored me like what is being described here.  

I didn't start having problems with him until he was an adult and married his wife the She-Devil.  He still was never openly rude but he started treating me like a polite stranger.  He claimed to think of me as his mother but he didn't act like it.  I got tired of the lies and we (me, husband and kids), are estranged from him now.  It's much more peaceful for me knowing that I don't have to see him or his She-Devil wife.  

I am or rather was a stepchild myself.  My dad remarried when I was 18.  I was happy for him.  He was lonely and she made him happy, which is all I ever wanted for him.  Just for him to be happy.  I never was rude to her or ignored her.  I included her in everything. He wouldn't have stood for anything less I don't think.  My mother as well, wouldn't have tolerated me disrespecting my stepmother or any other adult.  She and my dad raised me better than that.

Dad passed away 7 years into their marriage.  

My live in Skid never pulled this crap. Though he had no choice to pull this shit.  I tolerated no shit. One smirk, frown, etc.. .and my foot was proverbially up his ass. Fortunately, my foot had to beat his mom's foot to that destination.

He could not be nasty, he could not be disrespectful.  Why anyone would tolerate this crap from a kid or a kidult is beyond me. If they can't be respectful, they can STFU or figure out how to get a foot out of their ass. Period. Dot.

It sounds like before you entered the picture your wife and her ex were bad parents when it came to their children's feelings and emotions. Then including you and the other step made it worse. I'm sure your SS has a tremendous amount of resentment and guilt, along with grief, because he lived and his brother died. He probably gravitated to boxing to make himself feel stronger and protected because he didn't get that from home and he feels like he didn't protect his brother. Yes children misbehave, but kicking them out back and forth sends a message that your love is conditional and they aren't wanted. The only way for everyone (him, your wife and the ex) is for the parents to sit down and really own and understand how they failed as parents. It won't bring the brother back, but it might salvage the relationship with the son they still have. I believe the son is nice to the 1/2 siblings because he identifies with them as a child and he understands they are innocent. He doesn't want them hurt like he and his brother was. He deserves for his feelings to be validated and he deserves to be heard. Maybe in a letter, so he can open it when he's ready to receive the words. 

Sorry to hear the response was bad, it is to be expected considering all of the trauma. However, he opened the letter and he did respond. He could have thrown it away and never responded. He is clearly hurting. If he hasn't received therapy before he needs it. He needs a good therapist to help him talk out the trauma, grief and anger to forgive his parents--and himself. Your wife should give him some space and check on him through the sister. Maybe it will take a life event or major milestone for him to be receptive to reconciling. Maybe he will never get to that point, but she shouldn't give up on him. If she hasn't, I would also recommend a good therapist for her. I found one and she has helped me tremendously. By the way, you are doing the right thing. Be supportive and a shoulder to cry on. Getting directly involved will make things worse. For him, you are just an extension of his mom and he will treat you accordingly. 

Based on the parent model that my parents raised their sons with, a kid of any flavor including SKids, does not get to disrespect or violate the adult relationship at the core of a blended family, does not get to violate the sanctity of the blended family home, or disrespect either partner in that marriage/relationship. No one does.

These kids should face the wrath of Armageddon for disrespecting us, our mate, our home, or our family.

What seems to be a blank spot for many is.... as a SParent, our mate is the bio-parent in our marriage and we have full authority to end anyone who would disrespect our mate. If our mate is the SParent, same thing.  Our marriage, our partner, our home, our family, and ourselves are sacrosanct and anyone threatening those sacred things should be subject to pain, misery, and complete and total confrontation.

No one should be tolerated to speak to or treat a spouse in anyway but with respect.  Sure, they can be angry, hurt, etc... but they must be completely held to respectful discourse. Or.... suffer.

SS got lippy with his mom beyond my tolerance level when he was about 15.  I intervened, he cocked his fist back at me, he found himself on the wall with my fists at his throat  his jacket pulled tight around his arms and chest, his feet about a foot off of the ground spluttering, gurgling, and thrashing around, I held him up with one arm,swatted him on the back of the head with my other hand to get his brain reconnected, reached behind me and opened the front door, and spun him out into an absolute blizzard.  I then closed and locked the door.  His mom and I were shocked.  That was the first and only time things had gotten physical beyond a very rare swat to the butt when he was a tween.  We waited a couple of minutes and opened the door. SS was about 100yrds down the road barely visible through the heavy snow. He would take a few steps then turn to look to see if we had opened the door.  One of his shoes had come off in our struggle.   I waved for him to come back. He did.

We had a number of family discussions following that.

We took the same stance with the SpermClan, and even with my IL clan.  I would not tolerate any of them to disrespect my mate.  She would not allow anyone to disrespect her mate.  Neither of us would not tolerate anyone to disrespect our marriage