The sentence sounds unnecessarily long and convoluted to me.
I would say it more simply? For example, I doubt these shorter versions change the meaning much.
1. Unable to fulfill his dream himself, he tries to realize it through his son.
2. (After) Failing to do it himself, he is trying to realize his dream through his son.
3. After failing in his own turn, he tries to make his dream come true through his son.