Hi there. I have a suggestion. First off, I'd like you to know that almost every child here has the symptoms of ODD...lol. It rarely stands by itself, but is usually fueled by another diagnosis.
Autism Spectrum Disorders (ASD) (autistic spectrum) is VERY hereditary and if you have one spectrum child, you have a 1 in 20 chance that another one will have it. With the symptoms that your oldest has, I'd seriously take him for a complete neuropsychologist evaluation with an eye on high functioning Autism Spectrum Disorders (ASD). The neuropsychologist will test him in every area, in every way, in every possible situation (my son was tested for twelve hours). It is highly possible that your oldest son (and maybe youngest) are on the higher end of the autism spectrum, which can cause frustration, defiance, and very difficult behavior, especially if misdiagnosed, but those kids need Autism Spectrum Disorders (ASD) interventions as much as your middle one does, although he is more obvious. You say he had difficulties from birth. Did he cuddle? Make eye contact? Eat well? Does he tolerate noise, fabrics, and a lot of commotion without meltdowns? Is he "quirky" with odd behavior that maybe other kids have picked on? My son has high functioning autism and he was misdiagnosed a lot and put on tons of medications and given behavioral plans that all failed. Now that he has the right diagnosis., he has been off medications for four years and is doing GREAT (capital G GREAT, actually). I would take both your other kids to a neuropsychologist. Unfortunately, many psychologists and Psychiatrists don't understand Autism Spectrum Disorders (ASD) and have trouble diagnosing it--they see behavioral problems and often throw medications at a problem that needs other interventions. I'm of the "better to be safe than sorry" school of thought. I've never regretted forcing the school to give my then undiagnosed son Autism Spectrum Disorders (ASD) interventions. He would not be the high functioning young man he is today if I'd "waited." by the way, I"m so sorry for all the other stuff going on in your life. You don't need THAT too. Prayers are with you. Good luck!