A look at Natsuki Subaru, Natsuki Rem, Natsuki Rigel (almost named Vega, but Subaru he quickly decided against it as he didn’t want his son growing up to be stronger than himself) and Natsuki Spica.
The premise that Subaru and Rem fled Lugnica for the more Japanese country of Kararagi factors in heavily.
In fact, the bonus for buying the complete anime series on Japanese Blu-ray is a full 290-page IF novel.