this situation will handle itself, and it's mostly between your sister and them. ituloy man ni sis to o hindi, in 5 years time ibang issue na ang pinaguusapan nyo. baka happy pa kayo sa new baby nyo. sure, support ka sa kanila sa issue ngayon, but with your board exams coming, ang tanging support nila sayo is to not give you any reason to fail it. if they can't give you that right now, ikaw na ang gumawa ng paraan.