Im looking for a manga where the uke has a sister and both of them have heart disease and ...

Im looking for a manga where the uke has a sister and both of them have heart disease and he love his butler,his sister suddenly gave birth and ask him to take care of the baby while she is in the hospital and she won't tell who is the father then all of a sudden the butler said he was the father and he will marry the sister, that he's been using the uke all along...that's all i remember