Adekan
it's tagged as shounen ai but it's really bromance. I have read it all (=・ω・=)
http://www.mangago.zone/read-manga/hinatama/
http://www.mangago.zone/read-manga/uso_tsurezure/
http://www.mangago.zone/read-manga/mangetsu_monogatari/
http://www.mangago.zone/read-manga/sengoku_nights/
Princess princess
Ilegenes
I would recommend Lookism - although the bromance might not be as strong as you're looking for :)
komatta toki ni wa hoshi ni kike definitely. labeled shounen ai but nothing goes down (if u know wat i mean lmao) it's nice and long too... one of my favorites
Tbh manga like those are usually have the best place and good-looking guys lol. Here is my collection of goodness. http://www.mangago.zone/people/tag/49344/BL+undertones/
If you didn't already read, I definitely recommend Undertaker Riddle (=・ω・=) Mahoutsukai No Neko can work too.
07 ghost
Owari no seraph (this one have very strong bromance)
No. 6 (there's shounen ai though)
I want to read manga with bro romance I don't want it to be yaoi or shounen ai (well it's okay if they are). What I mean is I want to read a manga where there are two guys and their friendship is really strong somehow like Let Dai...