I think you are confusing the two witnesess with the 144,000.
It is the former who do the preaching and escape death, at a time whe people are being persecuted and killed for what these two are doing. They are indeed Jewish.
The 144K are the ones who were found faithful, who received God's seal on their foreheads. The next time we see them in scripture they are before the throne of God. Here they are singing a song which only they know, and as a reward for their courage and faithfulness in taking the name of the Messiah during the tribulation period. I don't believe anything is specificallly mentioned about their state of virginity.
The coming of Christ for His bride is portrayed in the parable of the 10 virgins. Of these, only the ones whose lamps were filled with oil (Holy Spirit, faithful)were able to go with the groom.