basicly 2 bi sexual sisters that love each other and their respective male partners
so basicly a fork
problem would be for the sis con sisters to even aknowledge the existence of males but the author covered that with a political marriage and good education on one side and the exposed secret and a 3way pact on the other. (there is no martial tag so counting on the description and the tag game she needs a 3rd party as the actual rider, the sole other possebility would be being a puff piece but that can be discounted when the description fits)
so from that point forward it should be a simple rom-com because all the pieces have been set
and i am a sucker for good rom com's