6: 2 the sons of God saw the daughters of men. The sons of God, identified elsewhere almost exclusively as angels (Job 1: 6; 2: 1; 38: 7), saw and took wives of the human race. This produced an unnatural union which violated the God-ordained order of human marriage and procreation (Gen. 2: 24). Some have argued that the sons of God were the sons of Seth who cohabited with the daughters of Cain; others suggest they were perhaps human kings wanting to build harems. But the passage puts strong emphasis on the angelic versus human contrast. The NT places this account in sequence with other Genesis events and identifies it as involving fallen angels who indwelt men (see notes on 2 Pet. 2: 4, 5; Jude 6). Matthew 22: 30 does not necessarily negate the possibility that angels are capable of procreation, but just that they do not marry. However, to procreate physically, demons had to possess human, male bodies.
MacArthur, John F. (2005-05-08). The MacArthur Bible Commentary (Kindle Locations 2203-2209). Thomas Nelson. Kindle Edition.