It is not your responsibility to 'keep trying' with his rude adult children.  If he wants eveyone to get along well, he will have to lay down the law with his adult kids that you are his wife and they will treat you with respect.  They don't have to like you but they do have to respect you.  

Agree with Evil - read up on disengagement on this site.  You don't have to have any relationship with his kids.

You don't have to like them ... they don't have to like you. Adults get to choose their own relationships. While it would be nice if everyone got along well, that's just not reality. Everyone must be respectful, though.

No need to keep trying. My relationship with my adult skids actually got BETTER when I stopped trying so darn hard. And your DH just needs to back off. I'd be upset with him that he's not doing anything to solve the problem, other than having YOU shoulder the responsibility. Heck no.

How would HE feel if he were forced to engage with a group of strangers (that's essentially what his kids are to you) and no one acknowledged him?

Ugh. Time for you to get angry at him for allowing his kids to treat you that way.

Also ss. They are disrespectful, answer back, guilt daddy for marrying me and having 2 kids with me. They are not people i want to be around especially when its non stop rants about bio mum and stepdad. 
 

my husband has asked me to forgive them because they apologized, allegedly to you but not me and frankly they are absolutely full of shitty behaviour i do not want to subject myself or my kids around. 
 

its been over 2 yrs no contact with sd's and ss refuses to acknowledge me despite living in our marital home, the one i cared for all our years of marriage

i have been married to hubby over 6 yrs and have 2 kids with him and sd's love to guilt him about his new family when they abandoned him for over 5 yrs. conveniently biomum was allowed to have an affair whilst married to my husband and marry the affair guy by making him leave his wife, such charming people.

i don't tolerate shit behaviour, you wanna be a shit, it certainly won't be around me

You asked if your DH has the right to be upset with you for not wanting to be with the SS & SDs. No, I don't think so, especially not after you've been trying to be kind and to connect for five years. Your stress levels have got to be through the roof by now and there's no reason to let the stepkids immaturity and disrespect affect your physical and mental health. I believe what you say about being a nice person and I'm sure your DH knows that you are a lovely person, too. SS & SDs are like predators who smell niceness and mistake it for weakness. Don't allow their vile actions to get to you. I've had some heart2heart talks with my DH and he finally (after about 4 years) got tired of his daughter's nasty behavior toward me. She brushed off his advice to behave herself around me, so he now supports and understands my disengagement. I don't go to their family events. If he wants to go to her house, I'm fine with having some "me" time. If she comes to my house (rarely these days), my DH makes an excuse for me while I'm away enjoying some free time. He often wishes to come with me since he doesn't even like to be around SD now that he is enlightened to her evil ways. I hope your DH will give you the encouragement and support you deserve.

You need to completely disengage. Stop trying to be friendly, and in fact go to your room when they visit. Don't cook dinner for them or do anything for them. These kids know exactly what they are doing to you and are intentionally trying to exclude you and pretend you don't exist. After 4 years of being in my bedroom watching movies that I enjoy when my husband's kids visit, I am just starting to sit in the living room while they are here. I tried everything to be friends with my step kids, including trying to buy love. It didn't work because my husband's kids believe if they are friendly to me, they are betraying their own Mother, who had an affair and moved 8 hours away to be closer to her married boyfriend. I don't try anymore and it's better for my mental health. I suggest that you and your husband read the book entitled, "Stepmonster" by Wednesday Martin. It was a major revelation for me because I thought I was the only person going through that nonsense. I have grown kids, whose friends like me. I wasn't accustomed to being treated like garbage. Oh, and I resented it!