How can i be less awkward around boyfriends family?

ive been asked to mind mt bfs dog whilst he is in wrk and his mam is away ,problem is i feel a lil awkward around his sisters and they will be home early when im in the house minding the dog one is 13 and the other is 17 and i am 20 one is in college the other sis is in school..i do talk to them but am a lil shy and so are they in some sense .il prob be left in the house with them by myself until my bf comes back frm work what should i do to be less awkward or do i just stay ot of the way?