When I told my parents that I was they were very understanding.(my niece told my mom).. When my mom took me in to make sure she told me that I had to tell my dad. I am a daddys girl and he was out of town, I call him and told him and he said that he would do anything to help me out if I needed it.. and I didnt think he would be to happy cause he had just been put in the hospital for a snowmobile accident that left him paralyzed. My whole family (my dads side) was very very help ful… I think you should have your bf’s sister and her bf listen to you and talk out what you want to tell them and how… that is what a couple of my friends did and their parents were very helpful… Hope this helps…
and Good Luck