The Ashton family was once one of the most powerful families in Hunter x Hunter, at least two decades prior to the present timeline.
There are four known members in the immediate Ashton family. The Ashton family has a son and a daughter that were roughly the same age (the son being one year older than her). Currently, they are all deceased - with the exception of the son, whose whereabouts are, as of this moment, unknown.
The Ashton family was a rich and powerful group, even among the key players of the Hunter x Hunter world. At one point, they shared a spot in the 100 most powerful families of the year. Ultimately though, their strength lies in their political power. Their standing in the social arena is such that they are apparently acquainted with world leaders, and the highest figures of different countries and autonomies (though the series also implies that they never liked big crowds; in which case, they might only associate themselves with this specific set.) Their influence and various connections are so huge and imposing, that even the Ten Mafia Dons of Yorkshin would rather not mess with them.
Rumor has it that their political acquaintances and friends were at their beck and call, and some of these were fearsome figures as well. Notable causes of intrigue include an ominously manipulative Senator who was corrupt (only by rumor - and was said to also have his own private army).
The husband and wife were government servants themselves, though of a different kind. At one point, they were secret agents working under a government agency. For unknown reasons (may be a mix of personal and classified reasons), they falsely gave up their work and went into retirement, presumably to operate covertly as key players in society, as well as to focus on other aspects of their life. Not shortly after their false retirement, they began to pick up fame.
One thing the public does not know about the Ashton family, was that they were acquainted, even connected, with the Zoldyck clan. They were related by blood, through Killua's mother who was the second cousin of the lady of the Ashton household. They knew this, though this was something the Ashton family was not willing to disclose, for fear that it might ruin their reputation. Still, they associated with the Zoldycks behind the scenes, and asked for help at times (none pertaining to assassination, ironically). For the Ashtons, as long as no one saw what they were doing, it was good. During this time, the Zoldycks were still able to keep a lie-low, despite having established themselves as a formidable force in the underworld. Consequently, they were still not as renowned as they were today.
At first glance, it seemed their relationship grew deeply and maturely, considering their families often interact on a daily basis, and that they co-worked in different aspects of their life - financially, socially, professionally, with a number of interesting projects and ideas the two families had in mind.
Over time, however, the Zoldycks were not blind to the observation that the Ashtons seemed to be loaning , even "hoarding" , from the Zoldycks , be it property, money, investments or possible sources of profit. By then, it might have been too late. It was not long before their true intentions were exposed.
In a deliberate set-up, the Ashtons managed to expose everything about the Zoldycks to the public. It could not be unseen. It was intricately planned, and the Ashtons knew the Zoldycks too well; they made their effective measures in a manner that the Zoldycks could not anticipate. It was a dark time in the family's track record, a time where an enemy was steps ahead of them and they were outsmarted - Zeno says he and Silva would rather not talk about it, and that he prefers they keep it out of the records.
It was a co-written "piece" by the two families; it was supposed to be a "fruit of success." It was supposed to be a social event organized by the Ashtons, with funds in favor of the two families. It was a great time - as always, each and every powerful figure would go, and they would feast. The Zoldycks would use the opportunity to hoard intel on established figures in society and spy, while the Ashtons would use their influence to put forward a number of people Zeno and Silva were assigned to assassinate. That was the main purpose they were there anyway.
Unbelievably though, the Ashtons had conspired, and Lady Ashton had managed to intercept what they believed were already guaranteed assaults, in turn, acting and manipulating the situation in order to expose the Zoldycks. The woman herself intervening was something the Zoldycks had not anticipated. Lady Ashton had taken the hidden attacks meant for the target, and in a pre-planned series of events, the Ashton's family-bound executive operatives identified them as the Zoldycks. Even as all this transpired, Zeno and Silva managed to escape, and they left stealthily and hastily. While they've done so, they knew things would never be the same again. A bond was severed - the ties between the two families permanently left, never to be touched again.
The Ashtons were never interested in the Zoldycks from the beginning, only what they had. Likewise, they were interested in taking everything from them.
Public awareness was first piqued here, as previously, virtually no one was aware of the Zoldycks' existence, even if only by rumor or legend. It was also here that the Ashtons imparted information that was meant to be kept classified for the meantime, regarding the existence of such assassins. It was here that some of the top figures in society were finally made aware. Despite breaching and breaking a rule set down by their agency, they were able to escape accountability through negotiations and covert manipulation, given the circumstances.
The Ashtons created publicity, making a public outcry of the situation. It had appeared as if the Zoldycks had intended to assassinate the Ashtons; they were framed. With the existence of the Zoldycks finally made public, and them at large, the government resolved to brand them as Class-A criminals with bounties on their heads. The Ashtons personally led the campaign after that "traumatic event", waging war against the Zoldycks to make sure they are captured and arrested, "and dead, if possible." For the remainder of the Ashtons' time though, they were unsuccessful, since the Zoldycks were still nowhere to be found earlier on.
The Ashtons' scheme was to put them down, then take everything from them - land, wealth, other property... all the power the Zoldycks ever had. Bringing them down and arresting them was also possible, but it was a chance the Ashtons didn't want to take.
The Zoldycks didn't need to kill them though; they had the job done for them. The Zoldycks were also acquainted with the high and mighty. Some of them, who invested in the clan and saw them useful for political assassinations, were not pleased with the Ashtons' actions. It also appeared some of these were the Ashtons' "friends"; it was due to this fact that they were able to get so close, have them killed and get away with it. News marked this area of history, known as the Ashton-Zoldyck incident, as one of the "politically dirtiest times of the decade."
Admirably enough, they left the Ashtons' only son alive. No one knows their ulterior motives, whether it be a developed fondness they had for the boy they'd already come across even years before. Between the conspirators, they left him because he was "innocent." True enough, he knew almost nothing about what was going on, and it would not be until several years close to present time before he uncovered the truth. He was found crying, hurt and confused, truly shaken by the series of events that had disturbed his family all along. He was eventually taken in by the local Department of Social Welfare and not much has ever been heard from him again. No one in the area has seen any Ashton since.
Rumors say the boy Ashton was adopted by another rich and powerful figure, which holds a bit of truth. He also migrated far away to a pseudo-isolationist country for the time being.