is kaoru really in love with his brother hikaru?

No, They're just playing around like...flirting?
I don't know but they're not in love with each other its more like acting in the host club, so like if you see them not around girls then they would act pretty normal

It's really just an act lol to impress yaoi fangirls

In Kaoru-kun and Hikaru-kun's case I feel that they're just acting and it's just for the customers/girls I know they like eachother as brothers but not in that fashion..well I don't think so anyway.

No he is in love with haruhi, in the manga kaoru figured it out before tamaki and hikaru and he told haruhi he loved her but wanted to give h her to hikaru because he loved his brother more. And Tamaki realizes it after Hikaru and Haruhi realizes she loves tamaki.

No, the twins are not in love with each other. It is just an act for the Host club to attract more girls. Besides, Hikaru is MINE!!! And Kaoru will be my best friend!!!

YESSSSS

Nah. It's just for fanservice. Like when the host flirt with the customers there it's just for fanservice and money.

Which is why I wouldn't go there. Because they just do it it for money and I would look and feel desperate.

tbh no one really knows but i think hikaru has a crush on his brother because in one of the episodes kaoru says "no way i lost again" the girls say "sorry kaoru" hikaru then says "now go easy on him princess,kaoru is quite the crybaby" kaoru then trys telling hikaru hes not a crybaby but gets cutoff by hikaru which says "oh so your gonna denie it huh,what about when the two of us are alone playing punisment games tell us what happens then kaoru~" .
this makes it like hikaru has a crush or a homosexual feeling for his brother