Consider this comparison: Abel and Jesus.
Both were shepherds.
Both were less acceptable in some sense. Abel was almost an after thought to his mother (Genesis 4:2). Jesus was certainly not the acceptable choice of the Pharisees, Sadducees, scribes, many for centuries since.
Both were killed by someone antagonized by them in some way. Abel and his offering were acceptable to God, which Cain apparently took personally. His thinking seemed to be "Because God has rejected me, I will kill Abel." Jesus was killed by the Pharisees, whose perspective and practices he attacked almost point blank. (Well, they KNEW it was point blank; this is a bit harder for us to see who don't live their social climate.) They're thinking went: "Because he has spoken rejection of us--as if he were God himsel--we will kill him."
Both of them have blood that speaks. Abel's blood cried out from the ground (Genesis 4:10). Jesus blood speaks of a better offering: "and to Jesus, the mediator of a new covenant, and to the sprinkled blood that speaks a better word than the blood of Abel" (Hebrews 12:24).
Abel is a picture of Christ, even to our first parents who had recently been kicked from the Garden of Eden (Genesis 3). Abel likely couldn't "save" his brother, but he certainly lived with an open hand and a humble heart before God. Jesus lived--indeed, lives--the same. Jesus' blood speaks a better word, one that covers us, one that cries out unto the Father in our behalf. He is not like Cain, who cared not about his brother when God asked him, "Where is Abel your brother."
Jesus is asked of the Father, and his blood answers. Jesus is his brother's keeper, and that is what we are in Christ... sisters and brothers.