I need some advice before my marriage fails.
My husband has a son age six. I have two daughters ages 5&6. We have one newborn son together.

My husbands son has behavioral issues. So much so that he throws chairs at windows in school & we get called to the school most days of the week.
I've been offering my husband ideas on ways to help, I've researched and read articles.i am also working with his sins mother to try and figure things out.

But seriously I feel like my marriage is going to fail if this cannot be worked out! Half the time hes letting him throw tantrums and hit things and talk back. He yells at adults he refuses to share with my daughters and yells at them and demands things from them and hits them. You learn how to share when you're a toddler. And its not just the normal issues all kids have with sharing, he goes wild and throws a tantrum when he has to share, stomps his feet, throws things, hits things, says he hates everyone, he hates sharing..so my husband has this thing he likes to do when his son gets in trouble. For some reason he has to include my kids in on the blame. Like if his son was doing something and it needs to be corrected and I tell him that he'll say,'she was doing it too!' Almost every single time when its not the case,..if that were the case like how he makes it seem at home she would be throwing chairs and we would be getting calls from her school too. There are clearly behavioral problems and obviously my husband must feel bad if every single time his son does something he tries to tell me my daughters are doing it too,...i can see what's going on with my own eyes!
Is there something I am not seeing please help I'm am getting so freaking irritated everytime we get him on the weekends I dread it and I feel like its hard to like him when hes a mean little kid,..he literally throws a tantrum every time he doesn't get what he wants. His grandma spoils the crap outta him, lets him talk back, buys him everything he wants,his mom didn't raise him the first two yrs of his life and drops him off at grandmas all the time,...just trying to give some background I do not know what to do!!!!!