Kassc - bless your heart. This sounds really painful. I think you meant to say your daughter is 6 months old, not 6 years.
I have three boys, and my oldest (when he was 2 years old) was picking on his infant brother. Thankfully it didn't last long and it's a distant memory, but I understand your feelings. But this CAN'T be allowed to continue. How children are treated by their siblings is the biggest factor in how they feel about themselves, and how they relate to other people. So this has to stop, today.
From what I've seen, and experienced, this is a two step process.
1. You and your husband sit together, and tell your son you love his brother as much as you love him, and you wouldn't allow anyone to pick on HIM for one moment, Just the same way, you are not allowing anyone to pick on the toddler. Period. If that means that the 7 year old gets taken to the babysitter while the family goes out to dinner, or has to stay in his room while the family enjoys play time in the living room, whatever. NO ONE picks on my kids, is the message. No one will pick on you, and you won't pick on your brother.
2. You need to make it obvious how cool it is to be 7 years old, and not a toddler. You should express to him how grown up he is, how he can (whatever it is) shower himself, fix cereal for himself, dress himself, read, whatever. " Wow, you are SO GROWN UP!! I'm so proud of how well you take care of yourself! I am here all day with babies and I have to do everything for them, but you are so smart and so grown up, when you come home I feel like I have help in the house." And then just beam at him, and ask some simple task, like can you go turn off that light upstairs? You may even be at the point of giving him HUGE privileges, like saying "I think you're old enough to go to a movie with a friend by yourself". You have seemed so grown up recently, do you want to choose a friend and I'll drop you off? (a matinee, and you make sure they're seated).
I'm sorry to run so long. I've just seen this problem before, and you have to do the carrot and the stick. Make it CLEAR you won't put up with even one more incident of abuse, and wow you're mature.
Best wishes.
You're welcome. And best wishes. I really hope this turns around, it's so difficult for everyone.
That`s a very good approach, RR. And sorry you have such a tough situation at hand, Kassc. A combination of firm limits and a new type of connectedness with your 7-year-old will hopefully do the trick.
I wanted to add that around age 7 a lot of boys seem to go through a cruel phase towards younger children, who knows why. It will be a great service to society if parents set limits at home when such behaviour first flares up. It so happens that in my neighbourhood two 7-year-olds tend to hang around toddlers and preschoolers. It did not take long until I realized they enjoyed poking or hitting or scaring the little ones as soon as they felt none of the parents were looking. Even though we were new in the neighbourhood, I jumped right in a few times and physically pulled the bullies away from the "crime" scene as the little guys were truly defenseless. Just by watching this, my 4-year-old learned that there is no doubt that bullying is not permitted. I hope he still remembers at age 7... My son now speaks up for himself and surprisingly the older boys do not dare to put a finger on him anymore but treat him like a real buddy. I still make sure I am always present in the background, though. Never will I forget that the also 7-year-old boy of my son`s babysitter once held a 20" butcher knife in front of his face when he was just a baby. Enough about myself...Kassc, I can imagine that, aside from feeling empowered again with methods RR mentioned - your 7-year-old could also profit from re-learning compassion and nurturing. My younger siblings were signed up to take care of two old horses for a while and another had the task to take care of the family car. Another one walked the neighbour`s dog and took care of two special plants. Eventually the joy of creating, nurturing, maintaining takes over and the destructive thoughts taper off. All the best.