Perhaps they time travel during the war with the Night King. They could use time travel as a strategic advantage. For instance, they might go back a short while to warn their troops about an ambush the Night King has planned. Or they could travel to a different location in time to gather more forces and then bring them back to the crucial battlefront to turn the tide of the war.
Another plot could be that they travel forward in time. They see the devastation caused by the Night King and then return to their own time with knowledge of how to defeat him. Maybe they discover a weakness in the Night King that was only revealed in the future battles. So they start preparing for it in their present, gathering the right weapons or allies.
One possible plotline could be that Jon and Daenerys travel back in time to before the Night King was created. They might try to prevent the events that led to his creation. For example, they could stop the Children of the Forest from using dragonglass to create the first White Walker. This would change the entire future of Westeros and prevent the Great War against the dead.
Perhaps Jon travels back to a time when the Night King was first created. He then tries to prevent the creation itself. This could involve complex interactions with the ancient magic and the people involved in that fateful event. He might have to make difficult choices and sacrifices to change the course of history and ensure the Night King never comes to be, thus 'winning' in a different way.
In fanfiction, one way it could be possible is through some sort of magical spell or ancient artifact. Maybe there's a long - forgotten Targaryen relic that has the power to manipulate time. When their child discovers this relic, it accidentally sends them on a time - traveling journey.
One possible plotline could be the struggle for the twins' inheritance. With Jon and Daenerys' complex backgrounds and the power struggles in their world, many might vie for control over the twins who could potentially inherit kingdoms. Another plotline could be the twins' unique abilities. Given their parents' special traits, the twins might have some extraordinary powers or a special connection to dragons or the North. For example, they could be the key to uniting the divided kingdoms through their charm and unique skills.
Perhaps Harry gets stuck in 1970 and has to find a way back. In the process, he discovers a long - lost magic that has been forgotten over time. He has to use this new - found magic in combination with his existing knowledge to build a time - travel device or find a magical artifact that can send him back to his own time.
Maybe Team 7 travels back in time to a period when a powerful and evil force first emerged. They then try to stop this force from growing in the first place. Along the way, they face challenges like not being recognized by the people of that time, and having to adapt to the older ways of doing things in the ninja world. They might also encounter versions of their own families or friends in the past and have to deal with the emotional turmoil of seeing them but not being able to fully interact as they are from different times.
In a possible plot, it could be that Daenerys has started to show signs of tyranny even while pregnant. Jon, being a man of the people and with a strong sense of justice, might feel that he has no other choice but to stop her. However, this act would be extremely controversial as she is pregnant. It could also lead to a civil war of sorts, with different factions taking sides based on their loyalty to either Jon or Daenerys. Her death could also have unforeseen consequences, like the unborn child having some sort of prophetic or powerful significance that is now lost, causing chaos in the world of the story.
Perhaps a plotline where they try to keep the pregnancy a secret at first. This could involve them hiding it from their allies and enemies alike. They might be worried about how the news would affect their standing in the various power struggles. Daenerys could fear that it makes her seem weak, while Jon might worry about the reaction of the Northern lords.
One interesting plotline could be their initial meeting being filled with suspicion but gradually turning into mutual respect as they realize they both have a common goal of saving the realm. For example, Jon might be initially wary of Daenerys and her dragons, but as they talk more, they find they can work together against the White Walkers.
In some fanfictions, the baby could become a unifying force. Since Jon has a claim to the North and Daenerys had a claim to the Iron Throne, the baby might be seen as a rightful heir to both. It could bring an end to the long - standing feuds between the different regions of Westeros.
It could also develop more complicatedly. Suppose they travel to a future where one of them has made a big mistake in the fight against the Night King. This could create mistrust or a power struggle between them. Maybe Daenerys blames Jon for something that went wrong in the future battles, and they have to work through that while still trying to deal with the Night King threat.