I've been thinking about this for a while and it all makes sense now.
Arthur and Allen's parents are business partners. They work in finances and do consulting and stuff on a freelance basis (I'm not too familiar with these kinds of jobs but I know they exist okay) so,,,, since they are partners of course Arthur knows Allen’s parents have a child but he never really saw Allen much because there wasn’t really a reason to
Skip a few years to when Allen is an aimless college student and home for the summer. or maybe longer, depending on his mood and ability to either find a job or the motivation to get his grades up. Allen's parents aren’t having that and want him to do more with his life, so they decide he's going to spend the summer as an intern. Since it's hard to find an internship when you dont want to find one, Allen's parents set him up with their business partner Arthur. they think it’s easier for him not to be insufferable when it’s someone else he works with. Arthur invites him for a pseudo interview to get to know Allen and and his… academic career.. He doesn’t get what he expected but hey, at least now he has this hot toy boy to screw when his wife’s not around. ✨ and that's how Allen ended up in an 'internship' that pays him a lot better than expected *wink wink* ✨
'but Riva how does Alfred fit into the story?' LISTEN.
Alfred somehow makes a shit ton of money, idk maybe bitcoin or he develops an app or whatever.. but he ends up filthy rich and with zero experience so he needs someone to take care of his finances - and that someone is Mr. Arthur Kirkland. Because Alfred occupies a lot of Arthur's time he ends up with his own office at Alfred's company. Allen visits Arthur at his Jones industries office or 'helps' arthur with 'work' as part of his 'internship' idk idc,,,,, but one day he runs into Alfred. and that's when the summer becomes even spicier for Allen.