States: Connecticut: Litchfield
I would say from the census evidence that Joseph and Stephen were brothers. You'd have to check Vital Statistics to be certain. I'd also say that Isaac is the son of Joseph, as in the 1830 census, only Joseph had a son in the 5-10 year old range. In 1850, Isaac stated his age as 26, so he would have been 6 in the 1830 census. Barbour's Collection of Connecticut Vital Statistics covers through 1850, so consulting those microfilms should clear it up.
Bill St. George