Phantasy Star: Fringes of Algo

So if Nial marries Alair, he moves into Dahlia and more or less abandons Landen (so it seems). If he marries Laya, he takes her to Landen instead of going back to her kingdom of Mystoke (and cleaning out the monsters there). What gives? Why couldn't he take Alair to Landen or go with Laya to Mystoke?

Nial preferred the view of his new Dahila home?

Or maybe he wanted to avoid having his brother-in-law harassing him at his own home, asking him money everyday, so he decided to move to Dahila and live on his brother-in-law's money.

Staying on Dahila allows Nial to take over Lune's throne, which ensures peace between the Layans and Orakians. It was a good way to bring an end to the aggression of Lune's forces and convince the Orakians he attacked that no more attacks would be forthcoming.

As for Mystoke... well, if it was Laya's original home, it is probably nothing like she remembered. It had been centuries since she was there. Plus the place seems to be in a constant winter. Given a choice between that and a more temperate area, I know I would choose the latter.

I like to think that the kings who might have authority over more than one kingdom would occasionally travel between some of the castles in the lands he rule. Instead of staying on Dahila all the time, Nial and Alair might occasionally spend a year in Landen. Everyone in Landen seems to know their son and be happy to see him there.