Domestic scenes are probably the most common type in spanking fiction. Unfortunately, this usually involves underage characters. Although entirely fictional, this should still make us uncomfortable. To be clear, what most spankos fetishize is the act of spanking, not necessarily the recipient being spanked. Despite this, underage characters are still pretty inconvenient at best and disturbing at worst.
I've considered this problem, and I believe I have a solution that I haven't heard proposed before. Many of my stories assume a social construct I am calling "graduated adulthood" as a backdrop.
Simply put, it's a rethinking of social norms that draws a distinction between legal definitions and cultural definitions. Under this fictional social construct, the legal age of adulthood remains eighteen, while the cultural definition extends beyond that.
Such examples do exist in reality to some degree in various forms already. The United States has examples going in both directions. While the legal age of adulthood is eighteen, laws in most states allow for sixteen year-olds to drive. Conversely, one cannot legally consume alcohol until the age of twenty-one, or rent a car until the age of twenty-five. Most seniors in high school turn eighteen prior to graduation but are still subject to school rules. In some schools, this can include corporal punishment.
The concept of graduated adulthood in my stories is more cultural than legal though. While an eighteen year-old in my stories is fully an adult, there is also a cultural expectation that they are still subject to parental authority to some degree into their young adult years. This authority isn't backed by any legal construct, but rather by cultural norms.
Therefore, in my stories, if a parent talks about spanking their eighteen to twenty-four year-old son or daughter, nobody really bats an eye at that because it's expected. This doesn't really apply to school settings, which is why my characters in these types of stories are usually seniors, meaning they are likely eighteen.
Of course, being a cultural norm means there is room for disagreement among characters. This can create interesting conflicts. For example, maybe a young adult believes that they are too old to be spanked, but they have a parent who disagrees. Culture is ever-evolving and therefore subject to these kinds of conflicts.
The reason I bring up this potential for more interesting storytelling is because I hope other writers of spanking fiction will decide to adopt this concept of graduated adulthood as well for domestic stories if such stories are going to have any sort of erotic elements.