It's not siblings, but chapter 4 of this manga has something like that: http://www.mangago.zone/read-manga/furachi_na_bokura/an/furachi-na-bokura-chapter-4(End).html/4/
@digi
nope they are siblings i remember i read something like that where it starts with the girl liking another girl but leaves her because her parents hurt the boyfriend of her gay brother and disn't want her lesbo lover to be hurt but then the brpther and his new bf and the lover go to the parents and say that they will marry so they marry each others partner
and eventually one brings up children topic but say they will do it all together ? Lol
is this the one you're looking for ?
Thou i don't remember the name since i read about a year ago
does anyone know of a manga that sound like this.its a yaoi and a yuri manga and there is a brother and sister who are gay are told by there parents to marry someone but thet decide to marry each other parners so the sister marrys the brothers partner and the brother marrys the sissters partner