Does the 'Sons of Jacob' refer to only Jews, or also Christians and Muslims? There is a song by Damian Marley that refers to "The sleeping sons of Jacob". I looked up 'Sons of Jacob' on Wikipedia and now understand them to represent the 12 tribes of Israel, but I have only heard "sleeping" sons of Jacob in the Damian Marley song.

I am curious to know what the significance of "Sleeping" may be, if anything. Is this a reference to some religious concept?
Having read the lyrics, I'm not convinced this has anything to do with the biblical Jacob at all. There is no other reference, except for an oblique reference to Israel. 

If one does assume that this is the Jacob who became Israel (hence Jews only), then the "sleeping sons of Jacob" would probably refer to the lost 10 tribes of Israel. After Israel was invaded by Assyria in 722bc, the northern tribes were dispersed throughout the empire and the known world. After that invasion, only Judah and Benjamin (the remaining two tribes of the Southern kingdom) retained any distinct identity as Jews.  Some parts of Africa (Uganda and Ethiopia to name two in particular) claim to be descended from these northern tribes. 

The idea that a once great part of western history is alive in Africa could be the spark the writer wishes to blow into full flame, that Africa might "wake up" and play a greater role on the world stage, as it did in the past. 

To get back to the Biblical issue, however, it is Abraham- Jacob's grandfather, who is the father of the Jews, Christians, and Muslims. 

According to both the Quran and the Torah, Abraham sent out Ishmael, once Isaac was born. Ishmael, and his birth mother Hagar made it to Egypt. Both traditions state that Ishmael was Abraham's firstborn, and Islam posits that Ishmael was also supposed to be the promised son of the Lord. Isaac, the father of the Jews  (through Jacob, later renamed Israel) and the Edomites (through Esau) is not a Muslim hero, whereas Ishmael is.