Psalm 45 is a marriage song sung for a polygamist warring King marrying yet another princess of another people (Tyre of Phoenicia) . It is impossible to definitively identify the original intended King but many have sought to do that. (Interestingly Ahab's marriage to Jezebel has been persuasively argued.)
The Psalm has stirred the imagination of Jews and Christians alike. Jews connect it with the Messiah as did the writer of Hebrews, who of course saw Jesus in that role.
17Instead of thy fathers shall be thy sons, Whom thou shalt make princes in all the land.
This line about the bride and groom having sons/ princes filling the role of their fathers, simply means inheriting the throne in a dynastic sense. The wildly ill fitting interpretation of the WT unfortunately isn't that much worse than the writer of Hebrews.
To identify this as a "prophecy" of Jesus should be offensive to Christians. Here we have a King disobediently marrying many foreign wives and the song revels in violence and extravagance.