I want to know if there is a way to essentially hook up two AUX ports from 2 phones and merge them into one. Allowing me to listen to the audio output from both devices at the same time and use any set of AUX headphones to listen to these 2 phones.
This works with splitters (and you can combine cables and splitters to get there, it doesn't need to be a single y cable with the right ends). I'd recommend against it however. Two outputs for one source is usually fine, but two sources to one output with just a y splitter can be detrimental. Depending on exact circumstances sound quality can be worse and/or it can (theoretically) damage your equipment.
For two low level sources it's probably fine in most cases, but definitely not recommended. There are positive summing circuits that prevent this, but usually the recommendation is to use a mixer instead.