You probably have received an answer to your question, by now, but I thought I would send you a reply.
My ancestor, Augusta Gallison, is living with the Gallison grandparents in Montpelier in 1850, as well.My Augusta (shown as Augustus on the census) is the daughter of Caroline Gallison, however Augusta was born in 1838 before the marriage of Caroline Gallison to John Bean. Have you come across Augusta in any of your research?
I believe that both Caroline and John died at the same time in Berlin, Vermont, according to this information on a cemetery in Berlin.Here is the link.The headstone indicates that they both died on the same day and of the same disease.This would have been in 1849, which would explain why the kids were living with their grandparents.Here is a link to the cemetery info:http://www.berlinvt.org/DEWEY-WRIGHT%20CEMETERY%20August%202008.pdfhttp://www.berlinvt.org/DEWEY-WRIGHT%20CEMETERY%20August%202008.pdf
If you can help me with Augusta, that would be great.