Even without the marriage cert I'm pretty sure that George was the son of James and Jemima from Colmworth.
I can't get too hung up over the 1841 census. There were two George Abrahams in Lincs aged 15 ie 15-19, both said to be born in Lincs. The one you mention in Haxey, and the one I mentioned in reply #12 below, who lived in Weston, Lincs. Haxey is 65 miles from Gosberton where we know George was living in 1851, whereas Weston is 8 miles from Gosberton. I know which one of the two I think it more likely to be, but as I'd never be able to prove it, and as it adds nothing to where George was born, I'd leave it if it were mine. There was was a George Abraham age 27 buried at Haxey on 24 July 1852 who looks suspiciously like the 15 year old George in Haxey in 1841, so if either is your George it looks to be the Weston one.
As Charlotte and Jemima were staying with her father in 1851 it explains why both are enumerated as absent in Gosberton.
Not sure what you mean about Jemima on the 1841 census. Ancestry has transcribed the surname as Abraham and that's what it looks like to me. They've transcribed her christian name as Jemma though. But what's odd about this census are the ages of Jemima, Ann and Mary, all of which seem to be understated by 10 years. I have the CDrom set of the 1841 for Beds, which is much clearer than the Ancestry image, and it's as I transcribed it in my previous message.
I've added the Abraham family to my LUGSDIN/Lugsden tree on Ancestry, and am adding children of George's siblings at the moment. James and Jemima seem to have been pretty lax about baptising their children.