"The Greek word (παρθένοι), translated unmarried (RSV), is literally virgins (KJV); but it is clear from what follows that the apostle has in mind the unmarried men as well as the maidens (Rev. 14:4). It may be that these are people who have taken a vow of celibacy" (Interpreter's Bible, page 84).
Now there's a lot in this brief quote that we can analyze. The Interpreter's Bible claims that the Apostle Paul is referring to both women and men in 1 Cor 7:25. Yet not all concur with this sentiment:
"Now regarding your question about the young women who are not yet married. I do not have a command from the Lord for them. But the Lord in his mercy has given me wisdom that can be trusted, and I will share it with you" (1 Cor 7:25 NLT).
"Concerning unmarried women I have no command to give you from the Lord; but I offer you my opinion, which is that of a man who, through the Lord's mercy, is deserving of your confidence" (Weymouth).
But the NET Bible renders this passage: "With regard to the question about people who have never married, I have no command from the Lord, but I give my opinion as one shown mercy by the Lord to be trustworthy."
The note for 1 Cor 7:25 (NET) explains:
Grk "virgins." There are three main views as to which group of people is referred to by the word παρθένος (parqenos) here, and the stance taken here directly impacts one's understanding of vv. 36-38. (1) The term could refer to virgin women who were not married. The central issue would then be whether or not their fathers should give them in marriage to eligible men. (This is the view which has been widely held throughout the history of the Church.) (2) A minority understand the term to refer to men and women who are married but who have chosen to live together without sexual relations. This position might have been possible in the Corinthian church, but there is no solid evidence to support it. (3) The view adopted by many modern commentators (see, e.g., Fee, Conzelmann, Barrett) is that the term refers to young, engaged women who were under the influence of various groups within the Corinthian church not to go through with their marriages. The central issue would then be whether the young men and women should continue with their plans and finalize their marriages. For further discussion, see G. D. Fee, First Corinthians (NICNT), 325-28.
The NET Bible therefore probably does not mean to include men and women "in the mix" (so to speak) when it chooses the rendering "people who have never been married" but primarily has women in mind. However, you have likely noted that the Interpreter's Bible includes Revelation 14:4 to apparently show that men are perhaps called virgins in that apocalyptic book. That's another testimony to how we should understand John's words in the Bible's final work.
In his NIV commentary on Revelation, Craig Keener writes that although male virgin language is rare, we do find this use in 1 Cor 7:25 and possibly in Revelation 14:4. Even though we may have a surface use of masculinity in 14:4, that does not mean all members of the 144,000 are males in the prophecy's fulfillment. But describing these Christians as male harmonizes with John's earlier vision in the same book:
καὶ ἤκουσα τὸν ἀριθμὸν τῶν ἐσφραγισμένων, ἑκατὸν τεσσεράκοντα τέσσαρες χιλιάδες, ἐσφραγισμένοι ἐκ πάσης φυλῆς υἱῶν Ἰσραήλ (Revelation 7:4 WH).
How are the 144,000 delineated in 7:4? As the "sons of Israel" (υἱῶν Ἰσραήλ). This wording along with the whole tribes scenario leads me to believe that "virgins" in 14:4 should be understood as having a masculine sense.