Sounds to me like this is a problem between you and your husband first, and his children next.
My opinion, and I don't know the whole story, is that you are an insecure wife because your husband puts his children before you in many ways, and isn't taking a stand and telling his children that YOU and HE are ONE, and that when they disrespect you they are hurting HIM and thier relationship with HIM and YOU.
But if he doesn't see you and him as ONE, (united above all else) then you are in a marriage that is really going to be difficult to build on.
Are you legally married to this man? Or living together? Because if he isn't committed enough to be even legally married to you, then you don't have a leg to stand on, his kids will always come first