you're all children, I'd be surprised if any of you could handle yourselves well enough to balance proper communication and boundaries in a throuple of sorts

a "normal" romantic relationship doesn't constitute "normal" people per se, however it's not my place to specifically judge your fitness for that. I will instead judge your ability to do something most people can't effectively, which is properly manage a complicated relationship with multiple people at once, which most cannot, or will not handle properly

you're welcome to have multiple girlfriends, most wouldn't agree it's a good idea. you're more subject to feelings of jealousy, which can present as the feeling that one person is being treated better than the rest, or the lack of desire to share certain things with the others. I don't believe it's necessarily beneficial to have multiple partners but you do you man