Your HUBBY also has to reinforce things.
They are old enough... I would, sit them down, have a formal "family meeting".... and clearly delineate the rules, TOGETHER with your Husband. AND the consequences. And stick to it. Regardless of their antics. The more they don't take it seriously... then you tack on another consequence or LENGTHEN the grounding. If they ask, a couple of hours later to go to their friend's house... you repeat, that is not allowed... then tack on ANOTHER consequence. ON both of them. They will learn... that THEY are making a "choice." And to cooperate or not.
Also, make a "contract" and have them sign it.
Take things away from them... privileges/treats/things, the use of the home phone etc.
Let them not take showers. Let them see how dirty and stinky they get. IF their Teacher comments, then tell them and they will be embarrassed. Take away their soap/shampoo etc., and then say nothing. If they ask you why its gone, say "well you don't take showers so you don't need it...."
Also, if you do a Google Search on "Tween Development" tons of good articles will come up. Read it for your and their benefit.
They aren't listening... nor following-up. You and Hubby have to be a united front. AND they are not taking you seriously, at all.
Every time they fight or bicker... tack on ANOTHER consequence on top of the existing consequences. Do it to BOTH of them, regardless of who started it. It takes 2 to start a fight and 2 to end it. Period.
The Tween ages are from 9-12 years old.... then they are Teens. I would get them on board before they hit the teens.
The book: "Have A New Kid By Friday" is real great. By Leman. You can get it from Amazon or E-bay.... it has great ideas.
Also the book: "How To Talk So Kids Will Listen, and Listen So Kids Will Talk."
try not arguing with them. Say what you want/expect of them. Say it once. Then if they don't do it... then on your own, write it down. Keep a tally. Then, based on that... put a consequence on them. Period. You AND Hubby... sit them down in "family meetings" regularly... to touch base, communicate about anything in the family, needs, budget, responsibilities, what needs to be done, what is not being done etc. Do this regularly. And make them a PART of it all.... and what the expectations are.
Make it about them doing their chores AND keeping their behavior in line. BOTH of these things.
Make it a 'requirement'... that EVERY day... they do something COOPERATIVELY... and to do something nice... for the family. To genuinely compliment someone else in the family, or to do something extra, something "thoughtful"... and that it be genuine. This will be teaching them "attitude" and how to think OUTSIDE of themselves. Too. Which they need.
They need to learn... how to act, beyond the perfunctory chores, and how to "act."
Just some quick thoughts,
All the best,
Susan