Billie Jean is not my lover
She's just a girl who claims that I am the one
But the chancer’s not my son

The story:

I think thi may be the real lyric anyway because where I come from the word 'Chancer' is given to an imposter pretending to be another persons offspring, usually for financial gain (i.e to inherit).

The practice that may have originated after the 1st World War when it was possible that there was a real possibilty that there was no one around to expose the imposter - you know, all persons who knew the real son or daughter killed in the war so the imposter is free to **sume the son's identity. Real Agatha Christie stuff. Hence 'Chancer' makes real sense to me. In fact even now when I hear this song, "the kid" doesn't sound right to me at all. I can only hear 'chancer'.