Hi there. I want to welcome you. All of our kids have at one time exhibited behavior of ODD. ODD, however, is rarely a stand alone diagnosis. You may want to do a signature like I've done below. I have a few questions to ask you that can help us help you. If we don't know any more about your son than you're telling us, that makes it very hard to help you. Here goes:
1/As either of your sons been assessed by a neuropsychologist? (That is the first thing I'd do--get both of them neuropsychologist evaluations--the diagnosis. on both of your kids are vague and not that helpful).
2/Do you have any psychiatric problems or substance abuse on either side of the family tree? Do the kids have violent tantrums, nightmares, talk about voices in their heads, have very graphic "friends" you can't see, get very upset when they have to change from one activity to another?
3/How was the kids early development? Were there any delays in speech? Any fine or gross motor delays? Did both kids focus on your face when little? Copy you? Point? Did they then and do they now know how to appropriately socialize with their age group peers? Any obsessions/Obsessive Compulsive Disorder (OCD) like behaviors? Any sensitivities to noise, sound, foods, clothes? Do they make good eye contact with strangers?
I've been around the block with myself (bipolar), my daughter (ex-drug abuser) and my son (high functioning autism). Of all the professionals I've taken all of us to, I find that NeuroPsychs got me the very best information. They test for 6-10 hours and actually TEST...they don't just take notes and ask questions and write prescritpions for pills.
Others will come alone. (I mentioned both kids because the older one seems like he COULD be on the Autism Spectrum Disorders (ASD) spectrum and I think it should be checked out. He'd get more services). Is the child diagnosed with ADHD actually MUCH better on his medication or doesn't it help or does it make him; worse? Is he ON medications??? I'm frankly not sure that changing your parenting w ill help if you don't get the diagnoses more pinned down. Until you can get a neuropsychologist evaluation. I recommend reading "The Explosive Child" by Ross Greene. It will give you some peace in the house until you can sort out what is going on with your little ones.