I don't have sufficient information to give an opinion regarding dividing the farm between you and your brother. You believe that if you don't divide the farm now, someone will
get hurt. Your brother believes that if you do divide the farm now, someone will get hurt. I don't know what harm either of you refers to, or why either thinks that might occur.
Also, while I gather that the property is still being actively farmed, I not sure of that. If it is being farmed, would there be any drawbacks to dividing it into two separate parcels?
Finally, what is the significance of your bother's wife and daughter playing a big part in his reluctance to divide the property. Why do they want to keep the property undivided? Why do you think their views are wrong?
I also don't know the legal form of ownership of the farm. It is some type of shared ownership, clearly. I doubt if it is legally in "joint tenancy." In joint tenancy, the surviving owner automatically inherits the interest of the deceased owner. I think you two own the farm as "tenants in common." That means each of you owns an undivided half share of the property, and you can each leave your share to whoever you want.
You could "force the issue" by bringing a lawsuit to legally divide the property. But this would surely cause hard feelings in the family. A less conflictual approach is to ask your brother to agree to mediation of this issue. Mediation is an informal process, facilitated by an experienced mediator, that can be very helpful in resolving matters like this. The mediator cannot compel any decision, but she or he can often help that people involved to break down barriers and find a mutually acceptable solution.