Because I Felt Like it

Thor

Thor will admit, reluctantly, that he didn't exactly have what you would call the correct reaction to Loki's gender fluidity.

Granted, he was rather young, and it was many centuries before his time on earth.

Odin said it was a phase that would likely pass soon, so Thor believed it. Then Odin said it was fine so long as it wasn't made a spectacle (read: done in public. They had a reputation to uphold as the royal family after all).

Eventually, the prince had grown used to his sibling's ever changing identity; viewing it as a quirk and "the god of mischief being the god of mischief."

Loki, on the other hand, had long since given up on trying to explain it. It's not like they needed Thor's approval anyway.

Thor will also admit, reluctantly, that it wasn't until he had come to earth had his view on that changed.

Though he may not be the most bright when it came to Midgardian customs and technology, he was always open to learn.

Concerning this topic, the young Spiderling was always open to teach.

Loki will never admit it, but as odd as it was for Thor to suddenly greet them one day with enthusiastic eyes and questions on labels, pronouns, etcetera, something deep inside them finally settled.

Not quite content, but understood.