Aegon, being a Targaryen, would have a certain connection with Daenerys. In a polygamy fanfic, they could potentially rule together. Arianne, on the other hand, could offer the support of Dorne. Daenerys might be hesitant at first about sharing power with Aegon and Arianne, but she could see the strategic value. Aegon could be the bridge between Daenerys and the Westerosi nobles who might be more accepting of a male Targaryen ruler. And Arianne could use her knowledge of Dorne and its people to help them gain more support in that region.
Well, in such a fanfic, Aegon could bring his claim to the throne. Daenerys, with her own powerful claim and dragons, might initially see Aegon as a threat. Arianne, being from Dorne, has her own political motives. Their interactions could be full of political intrigue. Aegon might try to form an alliance with either Daenerys or Arianne to strengthen his position. Daenerys could view Arianne as a potential ally in Westeros due to Dorne's history of independence. And Arianne might be attracted to the power that both Aegon and Daenerys possess, leading to a complex web of relationships.