Two souls permanently becoming one...

[Aloysius]

May I ask what is the motivation behind this?

The closest thing I have to an anecdote of this is some experiences I had of being multiple people at once. One time I had an experience where I was seven dudes at once (we called ourselves the "old gods" and me/Aloysius the "new god", it's actually a really cool story) and we were all standing around debating what to do with "me" (Aloysius), it's weird I'll say that much lol. That was a drug induced experience (I'm not advising drug use btw) so naturally it's quite different but it is the strongest memory I have of the phenomena (the others were all in dreams) and it was more of a lesson and a very symbolic experience but yeah that's the closest thing I have, hope it helps. The actual feeling of being multiple individuated beings is so unusual I can't even explain it.

I would advise the intentions and motivations be congruent in both parties involved in this endeavor, not just "oh yeah that would be cool" lol you could completely lose yourselves if this is possible, make sure you are aware of the consequences first. Also I'm not sure about the parameters of this in 3D, it sounds like a much more "natural" process for a higher density. But if you're both willing I ain't gonna stand your way, just be careful
Also I would advise resolving inner conflict in both parties as well, you may even find that once the self and other self is appreciated and respected as is, there may be no desire to change either, maybe lol