Of course we all focus upon Eve's seed for obvious reasons: 1) Men, not women, provide the "seed," while women provide the "egg" in human reproduction; 2) Jesus did not have a human father (Mt. 1:16, 18-25; Lk. 1:26-35; 3:23); and 3) Angels do not reproduce (Mt. 22:30; Mk. 12:25). But isn't it ironic that we can so easily believe the "exception to the rule" that a spirit being (in this case, the Holy Spirit) fathered a human child through the Virgin Mary, while we are closed to the idea of another spirit being (Satan) fathering a son through a woman, such as the Mother of Harlots (Rev. 17:5)?
Since Satan, according to Genesis 3:15, will have a descendant, is it not possible that the "sons of God" (here presumed to be the fallen angels) could have mated with "the daughters of men?" They no longer appear to have lived in heaven, but only "visited" at certain times (Job 1:6; 2:1). Perhaps the "rule" for them changed when they were cast down to the earth (Gen. 3:14; Ezek. 28:16-17; Lk. 10:18). Who knows? A much better question is, of whom does the Scripture speak as being Satan's descendant?
One thing for sure, whoever he is, he will be the opposite of Jesus Christ, and yet he will come pretending to be Christ. The one who immediately comes to mind is the Antichrist (Dan. 7:1-25; 9:27; 1 Jn. 2:18; Rev. 6:2 w/ 19:11). He is also known as "the man of sin" and "the son of perdition" (2 Thes. 2:3). The word "perdition" means "destruction" or "judgment" (Rev. 17:8-11). Two prophetic types for him are found in Antiochus Epiphanes (Dan. 8:5-13), and in Judas Iscariot (Jn. 17:8-11). And finally, he will be known as the Beast (Rev. 13:1-10)!
All who deny Christ are known as antichrists (1 Jn. 2:18, 22; 4:3)!