tho i feel like he doesn't have many ships lol

As far as I'm concerned any defined friend group is a free polycule, but I do have some thoughts.

Twice always struck me as a character that seemed dissatisfied with his shortcomings as a functional adult. Because of that, he tends to gravitate to people that seem to have it figured out; whether that's actually true or not.

Hawkstwice (personal fav) would have been so adorable in another life. Given that a lot of Hawks' confidence is a front, I think they both needed a moment to drop their walls to someone that they just never ended up getting. Their ending in canon adds a beautiful tragedy to it if we're talking canon compliance.

Dabi (either alone or added with Hawks ♡) is a bit gruffer with Twice but, again, this man only speaks in gaslighting. He is a sensitive little baby that has never felt the gentle touch of a lover. He arguably needs this more than Jin does and his antics could definitely wrench out a softer side.

For slightly less dramatic options though, I've always headcanoned Magne got that Big Sis nickname so early on because she was the oldest one in the action squad and she only ended up reinforcing it by being so wise with her life experience. She actually has figured out what she wants for herself and her struggle largely comes from society discouraging her choices (i.e. beating up transphobes) so, she became the one to go to for life advice. Twice is genuinely really smitten with her and on top of being a good friend, she's big and strong and cool! I can see Twice tucking himself close to her a lot, not necessarily for protection but even if you can handle yourself, a little extra security never hurt. Of course, she does die to Twice's mistake but hey, I said slightly less drama.

Togatwice isn't usually my go-to mostly because I find the fact that everyone in the league treats her more like a little sister/daughter absolutely precious, but I think they'd be a cute couple! Contrast to Magne she's a lot more hyper and chipper. Where Magne can have a deep uncomfortable conversation with him, Toga can distract him with something fun and light. Every scene that goes back to her handkerchief is just so adorable. Her genuine care and understanding for him breeds one of the best fight climaxes in the series for a reason.