Help. dont know what to do. boyfriend prob?

my boyfriend wants our parents to meet each other, ordinarily this would not be a problem but my boyfriend is really serious, and well i'm not. he is 6 years older than me and he is talking about moving in with each other and buying a house and a dog and all that kind of stuff. i'm 20 for god sake and i don't want to get married, he keeps asking if i want to get married and i've told him i don't. he is really serious and this is his first long term relationship (we've been together 3 years but i don't see it as serious). i don't know what to do. i don't want to get married! his sister just got married and he is in the whole wedding mood. how do i get out of his parents meeting mine and further fueling his deranged mind? HELP!