Your husband's heart is breaking and he's kind of in panic mode because his son is doing so miserably, and it's his fault and his ex's fault that he's on such a rocky path.
His dad has gone off and married someone else and created a separate family, his mother isn't good at supervision, he's a lost child.
Mumbling disrespectful things is just a dot in this picture, always. The bigger issue is this child doesn't care what happens to him, he's unmotivated, he's failing in every aspect.
THAT is the issue, not whether he mumbles and doesn't act normal. He's not normal. He's ripped apart.
I agree with those who say you should just ignore the behavior completely, don't take it on yourself to discipline him, leave that to his dad. Mumbling is nothing.
When your little boy is that age, you'll understand your husband's despair and fear.
Sorry to hear about all that! It's really sad that some women can't just let go of their ex's and let them be happy with someone else when they are miserable. The best advice I can give is to completely stay out of the way. Let your husband deal with her, that way you can't get in trouble for things you haven't done. If your husband has to pick up his son for visitation, let him go alone. And don't let his son get to you! If he says something under his breath, try to shrug it off and don't let it bother you. I know that can be hard, but if he knows it bothers you, he's going to do it more out of spite (or by his mother's influence). I'd be sure to let him know whose boss though! He's only 13 and he is NOT going to control you, your husband, his mother, or your child. He's a child himself and he needs to respect his parents whether he likes it or not. The mother is, I'm sure, a lost cause! That is, until she finds a man or a hobby to free up some of her alone time. It's really sad to watch adults act like children, then they wonder why their kids act out! I'm in a similar situation, so I sympathize! I hope it all works out for you. Please keep us posted!
i have tried the approach with the parents of the boy but his ex is mad because she still hasn't found love and so she is always putting me down to all involed and they refuse to communicate and when they do it is like ww3 and i always get stuck in the middle she has had me arrested for everything her and her friend can think of stuff i did not have anything to do with such as assault vandilism etc..... i just want to give up but i love my husband and son but sometimes the extra baggage is to much when i try so hard
First of all, this is NOT your fault. Your stepson is the one with the problem and your husband should not allow it. I know this sounds cliche, but your stepson is probably going through a phase. He's at that age where he has no parents, no authority, no rules whatsoever. Your husband should be sticking up for you too. He shouldn't allow a 13 yr old to have that much control. And of course, a big part of it is his mother. Your husband and his mother should work together when it comes to raising him instead of playing the "I'm going to get you back" game. It sounds like there is a huge lack of communication between the two parents and one or both need to step it up with him before it's too late!!