Do you think this guy is serious about dating or just being manipulative?

i have a guy friend who always tries to coax me into having with him. i tell him no for more than one reason. one reason is that i want an actual relationship, because i'm 27, and in my future, i want there to be a loving husband and my future biological children. the second reason is that i'm not a tramp, and i don't know what women or how many women he may have been with. i told him all this, and he asked me shortly later if i wanted to date. and then he also said that we would have pretty children, even though he told me before that he didn't want children or marriage. now when i mention how i want my future to be he says "well i asked you if you wanted to be my girlfriend". this is a 39 yr. old man. do you think he's really serious?