For example: When Joe sets the table for a week (cleans room, etc. ), he can play Nintendo for an hour on Saturday. When Saturday comes, it is up to you or your husband to say in a calm, non-punishing voice something like, "Because you chose not to set the table on Thursday and Friday, you may not play Nintendo this weekend. You may play next Saturday if you choose to set the table every day." Do not argue about it. Just make your statement and walk away. I encourage you to look for creative consequences, not punishments, and keep your expectations that the child can and will behave appropriately.
The age and background of the new additions to your family are circumstances that ensure it will take time, patience, and love for them to change. They will have to learn new skills and this implies many falls, frustrations, and starting over. The boys have not had limits put on their behavior and when you do it, they will be defiant. All kids at one time or another push back. That is their job as adolescents. As a parent you will have to remain calm and not take their defiance personally. That defiance will lessen and disappear as they learn your expectations and get a chance to have their say even if they don't always get their way.
It's important to have family meetings where everyone (Mom and Dad too) get a chance to develop the rules and consequences. Plan family experiences -- fishing, a trip, movies, picnics. Make a date with each individual boy to do something special with him. Kids of all ages love that even if they do roll their eyes!
Since school will be starting soon, I encourage you to talk with the boys' school counselor to see if there are groups or programs that would help them. For example, a grief group might be very appropriate since they have lost both their father and mother. Both boys might find support in a prevention group (discussion of issues around drugs).
Finally, if there are parenting skills groups or classes offered in your community, I urge you and your husband to enroll in them. There are also some excellent books at your local library on parenting.