ANOTHER THING I HAVE THOUGHT A LOT ABOUT thank you for the question!!

our only established Parental Lore is that they were "normal", lived on a tiny island w/ no other kids Ardbert's age (so probably not a lot of young families), and that his dad knew how to raise amaro + taught him how- so they probably owned at least one. I've settled into the headcanon because of this that they were quiet, reliable folks. The sorts of people that you could only visit once every ten years but nothing in their house or habits would ever change- same garden, same routine, same old amaro chewing grass in the yard. The sort of people that would seek out a life of near-complete solitude on an island only barely big enough for what could be considered a "town". (if anything- a central store, a town hall, some little market setup for selling what each farmstead grows or makes)

people that, in all honesty, probably had an extremely hands-off take on raising a child! some things would be necessary (no kids his age means there certainly wouldn't be a school, so his learning to read or count would need to be homeschooled) - others would be practical, or as a form of bonding. i imagine his father was a softhearted sort of dude that would teach a kid to take gentle care of creatures, the kind of treatment Ardbert shows Seto later, when he finds Seto abused and malnourished- a softspoken, humble man who bonded more through teaching and silence than lively conversation. i can't imagine his mother was that different, though SOMEONE had to teach him to read and write so it may well have been her, challenging her kid to reading and spelling out words at the market to keep him from running off.

as far as the ongoing relationship- Ardbert was a busy guy who always traveled and had a host of friends as his acting family, so I can't imagine he went home much, but with parents and a home like that, there wouldn't be much reason to! I like to imagine he wrote home now and then, and certainly sent along money or gifts when he found something practical enough that they might like it, but he's described them in writing as quiet lives- people who exist in their own universe, entire lives that could be lived and die and few if any would ever realize they were there. no less important for their lack of raised waves, but never able to fully comprehend how big the world was, or how important in its fate he had become. it was something he loved them for- always treating him like their funny wayward son, and his friends like extended family- but the island would never be more than cramped and stifling when his love lied with the world beyond.

unfortunately for him, tiny islands were the first to sink when the Flood irreversibly stole the tide from Kholusia's shores. if it wasn't the flooding, it was the sin eaters- doing as tiny lives do, and disappearing before he realized to look for them being gone.