You'll notice the phrase daddy issues peppered throughout this learning guide. There are quite a few patriarchs in this novel—Cyrus, Adam, and Samuel—and in each case these characters stand in as god-like figures for their children. Now you might be wondering, "Wait, if a lot of this story is about Cain and Abel, isn't Adam their dad?" Yes, dear reader, he is; but in the biblical story of Cain and Abel, the real disapproving father figure is God.
God, both in the biblical Cain and Abel tale and in East of Eden, is like the ultimate authoritarian dad. He's scary, you don't want to make him angry, and you wish he would just give you a hug but he's never going to. We definitely see that in the Cyrus-Charles and Adam-Cal relationships (i.e. the God-Cain relationships).
But God has his favorites too: he likes the people who give him nice things, like lamb kebob or puppies or the pride of having a kid in college. It's pretty arbitrary what God/God's stand-in likes and what he doesn't like; we mean, fifteen thousand dollars seems to be a pretty nice gift as far as gifts go, but Adam just doesn't feel it.
With Samuel things are a bit different. He's less like the God of the Hebrew Bible and more like one of the patriarchs, like Abraham, or a leader like (hey, why not?) Samuel. In fact, patriarch is exactly the word that Steinbeck uses to describe him:
Adam saw a big man, bearded like a patriarch, his graying hair stirring in the air like thistledown. (13.3.33)
Hm, a big, bearded, biblical patriarch with lots of children who go off and do various impressive and not-so-impressive things. Sounds a lot like the Israelites to us. So Samuel is less of a picky, imposing deity-dad and more of a grand paternal figure spawning generations of Hamiltons.