Maybe you and I could start an "Evil Stepmothers club " . My husband is the same way , he ignores the problems and tends to "not hear" the conversations and "not see" the actions his kids do or say when they are around . I do have to say his daughter at least , after years of spending weekends/weeks up here while he's been gone , has started to grow up a little . His son ( almost 22) dropped out of school , has no drivers liscence , and was fired from his first job after 2 weeks because he was "sick and his friend didn't call the employer to let them know he wouldn't be in for a couple of days . He lives with his mother ...no bills to be paid...in fact she gives him $200 a month . My husband has been out of state for almost 8 months . He did come back for Christmas and had to almost beg his son to come spend time with him. I didn't want my stepson there . He's a druggie , and only comes around when he thinks he's going to get something from someone . My stepson opened his gifts , and like yours , there was no thank you . He did however pocket the money ( which I told my husband not to give him because all he does is spend it on drugs and alcohol...this being told to me by his mother that he lives with and his sister ) . 
Long story kinda short...if your hubby is anything like mine , then yes , you need to be the evil stepmother . It's hurting your hubby just as much ( if not more ) by having them around . My advice...COMMUNICATION . You need to tell hubby about everything that goes on...you don't want to risk losing him over something so stupid . Convince him that he NEEDS to start setting rules , or he's gonna have one unhappy wife . It takes time...but I can see after 4 yrs that my hubby is finally understanding that I'm trying to help him , our relationship , and his relationship with his kids . Don't ever be affraid to tell your hubby how you might react to certain situations his kids put you in , but also try to be aware and listen to his side of the story . I've noticed since I've been more strict , and setting more rules that my stepkids respect ( well more than they did ) my house and my rules . I don't care what age they are....you still have to respect your elders and other peoples property . Hang in there girl......stick by what you know and what you believe !