Talk about opening a can of worms! Are you ready? Cuz when I create fanbabies, I don’t joke around XD
I actually designed a Seiya/Usagi fanbaby years and years ago that I only posted about once. But the truth is I had an entire backstory worked out on Seiya/Usagi’s relationship post Crystal Tokyo. You can still see some concepts for it in my DA gallery (most of which were just Kinmoku fashion). Since it is unlikely I’ll ever have time to get around to actually writing it I’ll just do a summary on their kids:
Princess Hikari— “Sailor Moon Fighter” is a result of an illicit love affair between Neo Queen Serenity and Seiya whilst they were visiting on Kinmoku. After they parted and Serenity returns to Earth, she discovers she is pregnant with Hikari. Since both Seiya and Endymion shared similar hair and eye coloring, Hikari looked close enough to Endymion that no one questioned her parentage.
When Empress Kakyuu and her Starlights visit Earth several years later for Chibiusa’s coronation and marriage to Helios, Seiya quickly realizes that he is Hikari’s biological father. This is undeniably confirmed when she awakens as Sailor Moon Fighter.
Hikari herself is a very mature and perceptive for her age. Even though she felt she never quite fit in especially with Endymion and her role as princess, she always tries her best to never disappoint, and is a bit reserved. She actually shares a very close relationship to her half-sister, Chibiusa to whom she always looked up to. It was in trying to protect her elder sister during the coronation that caused her to transform to “Moon Fighter” and much to her deep regret resulted in causing a rift between them as it revealed her true parentage. Eventually, she leaves with Usagi and Seiya to traverse the universe after Usagi separates from Mamoru on mutually amicable terms. (especially after both parties feel that they’ve fulfilled their destiny, the well being of Crystal Tokyo is secure with Chibiusa, and they are both finally free of obligations)
Despite finding happiness with her new family, she always felt unwavering loyalty to Chibiusa and eventually returns to Earth—not as a Princess, but to serve as one of the new Queen’s Senshi, and the two reconcile. Even further down the line, she will become close friends with the fairy, Perle (Peruru). Hikari’s name means “light.”
Aika—“Sailor Star Singer” is Usagi and Seiya’s second child. She was born not too after they started their travels. Because her family is rather nomadic and adventurous, Aika is used to living a carefree lifestyle. She is definitely more tomboyish than her elder sister, and her constant cheerfulness can sometimes bulldoze and overwhelm others to exhaustion. She can also have a quick temper but forgets grudges easily.
When Aika awakens as a Sailor Star Singer, she chooses to live on Kinmoku. There, she befriends and becomes close with Ami and Taiki’s daughter, and fellow senshi, Sailor Star Seeker. (eventually she will also gain the ability to switch genders at will). Despite her new role as one of Kinmoku’s Starlights, Aika still gets bouts of wanderlust now and then, and is considered untamable by a lot of friends. Aika’s name means “love song.”
—-In some of these sketches, especially in their family shot, you can see their clothing fashion is pretty inconsistent. This is mainly because they’re star hopping so often they adopt whatever foreign fashion is available to them. Even after their children choose their own paths, Seiya and Usagi are happy to continue to travel the universe together and experience new things.