/ara/-tan is mostly a traditional mother figure. She lives with her son, who is unnamed and simply referred to as Shota-tan (despite the name he can vary anywhere from child to late teenager), but there is no father figure present - whether she's divorced or a widow is deliberately kept vague. She dotes on her son, and can get too physically affectionate with him at times, but at least knows these urges are wrong and tries to keep them contained (not that she's very successful at it). How Shota-tan feels about their situation isn't specified, but he doesn't seem to put up a fight when things get out of hand.
Despite their overlap and the board having an interest in it, /ara/ and /ss/ are different things, so /ara/-tan's options aren't limited to Shota-tan. She can help herself get relief using her trusty dildo, "Kirby", and her yoga partner Mrs. Mocha can also give her quite the workout at times.