Pretty sure it's one of the mangas here: http://www.mangago.zone/tag/Master+x+Servant/?page=3
Is it something like this http://www.mangago.zone/read-manga/1_2_cigarette/
No. There are actually two like this manga one cute one with the two brothers (half brothers I think) that actually have a good relationship, but both end up dating their respective butlers' bodyguards/attendants'. The other is more psychological with identical twin brothers where both brothers fall for the cute uke (attendant/ butler) and one dies and the other takes up his identity but the uke only finds out towards the end.
No, i'm sorry for having such a bad memory. ( ̄∇ ̄").
The first one from what I remember: The two half brothers have a good relationship, the uke (the younger bro) and the seme (the mc) were childhood friends and mc was something like his bodyguard rather than a butler. The uke and his brother are both not from Japan ( but I think the uke is half). The uke leaves Japan and goes back to his country but comes back to be with mc. Mc's family are all martial artists and have a history of protecting the uke's family (i think?). Anyway, his bro is dating his own attendant/ bodyguard and encourages the uke and seme to be together.
The second story is about uke (mc) needing a job and money. He goes to this recluse guy's house and the guy offers him the job of looking after him (being his assistant/ caregiver). They both fall in love with each other but the guy is sick and dying, but mc does not know this. Mc goes away for a few years (I think one of his family members were sick and he was saving money for them and he goes to look after them). When he comes back the man (seme) he loves seems a bit different but mc loves him anyway, at the end after they become a couple and are all lovey-dovey happy does mc find a letter explaining that the man (seme) he loves is not the one he originally fell in love with but his twin brother. But the seme says that originally it was his brother's dying wish to look after the uke, but the seme like his brother fell in love with the uke.
This is from the second story right?
http://www.mangago.zone/read-manga/bokutachi_futari_ga_koisuru_riyuu/
Reminds me of another manga with a similar plot (minus the omegaverse part), where one brother was a playboy who had a sexual relationship with his attendant and the uke ends up with the other brother who is a recluse. Both brothers lived in the same mansion.