Rhaenyra was perfectly capable of having kids, and she had five healthy sons. Laenor didn't have children because he didn't want to, not because he was incapable (as in he was impotent, sterile, or had a condition that lowered his ability to sire children, such as undescended testicles, hypospadias, or chordee.)
Laenor's funeral was held at High Tide. During the civil war called the Dance of the Dragons (129 AC - 131 AC), Laenor's three sons by Rhaenyra all died. However, during the Sowing of the Seeds, Marilda of Hull brought forth her two sons, Addam and Alyn, claiming them to have been Laenor's bastards.
Jacaerys, Rhaenyra's eldest son, and his two younger brothers have spent their short lives surrounded by whispers that their real father was Ser Harwin Strong. It's an open secret that these “strong” boys aren't the sons of Laenor Velaryon.
But we know exactly why those kids aren't Ser Laenor's, and it's not exactly subtle to the rest of the court. In fact, Ser Criston knows with certainty that Laenor is a gay man. Rhaenyra has no desire to sleep with Laenor if he doesn't want to be with her, and forcing him or her to do that would be atrocious.
Ser Laenor and Princess Rhaenyra had three sons, Jacaerys Velaryon, Lucerys Velaryon and Joffrey Velaryon.
So in addition to Rhaenyra's three sons with her first baby daddy Harwin (RIP), she has one daughter and two sons by baby daddy two, Daemon. Visenya, the daughter, is Daemon and Rhaenyra's firstborn child together.
Rhaenyra Targaryen: In episode 2, Viserys mentions his daughter, Rhaenyra, is 15 years old. Then, following a time jump in episode 3, he mentions she is now 17 (and “of age” to marry).
Even Laenor, Rhaenyra's husband, hints that he knows the princes are not biologically his children in Episode 6. Despite the seeming acceptance of the children's true parents, whispers in the Red Keep intensify following Harwin's fight with Criston, the latter of whom teased the former about his secret fatherhood.
The shock of the loss of her father, combined with the Greens' ruthless betrayal sends her into early labor. Without modern medicine, a baby born so early had very little chance of survival in the best of circumstances - and in these terrible conditions the baby, a girl named Visenya, is stillborn.
Rhaenyra was perfectly capable of having kids, and she had five healthy sons. Laenor didn't have children because he didn't want to, not because he was incapable (as in he was impotent, sterile, or had a condition that lowered his ability to sire children, such as undescended testicles, hypospadias, or chordee.)
Like Laenor Velaryon's sexuality, it was a “known secret” in the Red Keep that Harwin Strong was the father to Rhaenyra's three children: Jacaerys, Lucerys, and Joffrey.
Rhaenyra and Daemon both know Laenor is alive, and faked his death.
Daemon shows his genuine care and attention to Rhaenyra several times before the two marry. This doesn't take away from the many destructive and inappropriate parts of their relationship, but the books imply that Daemon does love Rhaenyra.
In 196 AC, the year of their marriage, she painstakingly produced a set of twins, Aegon and Aella. Another set, Visenya and Valarr, came in 197 AC. After her troubled deliveries, it was said Rhaenyra had nearly beaten a serving girl to death for having claimed the princess would die in labour.
Rhaenyra's three eldest sons all died fighting during the Dance of the Dragons, but her two youngest sons, the sons by her second husband, Prince Daemon, survived the civil war.
Rhaenyra's baby did end up having scale-like defects and a malformed body in House of the Dragon, which aligns with the occasional reports of Targaryen women bearing dragon-like stillborn children. While House Targaryen professes to have the blood of the dragon, this wasn't thought to be intended literally.
Daemon shows wife Rhaenyra the message; she recognizes that if Luke's claim to the title is questioned, so could the legitimacy of her three sons with Harwin Strong. Daemon puts a hand on Rhaenyra's belly. She is pregnant with their child.
House of the Dragon: Daemon and Rhaenyra's children, explained. Daemon and Rhaenyra share two children together: Aegon III and Viserys II.
This clears the answer to the question. It was Criston Cole to whom Rhaenyra lost her virginity. While Dameon (literally and figuratively) introduced her to the world of sexual pleasures, it was Criston Cole who was the object of the expression of her desires.
It isn't explicitly stated in the show, but because we learn after episode six that all three boys have dark brown hair — and despite Rhaenyra and Laenor's matching blond color — it has been strongly implied that they are actually the children of Ser Harwin Strong, the Lord Commander of the City Watch.
Sons of Rhaenyra are indeed bastards. The most important distinction is that Rhaegar has silvery white hair, whilst her three sons have brown hair rather than the trademark black hair of the Targaryens. They are the illegitimate children of Ser Harwin Strong and Rhaenyra.
Princess Visenya Targaryen
Ultimately, Rhaenyra has two husbands (not at the same time) and gives birth to six children. Meanwhile, it is disputed in the book as to whether Rhaenyra ever consummated a romance with Ser Criston Cole, but either way, the two go from a close relationship to enemies.
So, let's agree that he is (give or take) 16 years older than Rhaenyra. This places him in his early 30s when we first see him meet his niece. Yes, his niece. His teenage niece who we immediately realise he has a bit of a thing for.
The story of the princess and her valiant knight did not end as a fairy tale, though. A sordid and controversial story began to spread that Rhaenyra lost her virginity to her uncle Daemon at age 16. No one knows if that is true. But Targaryens had long married within the family to keep their bloodlines pure.