Help!
If I understand your post, Christian Kellar Sr, was married to Anna Maria Hart in 1824, and had children, Valentine, b. 1808 and Christian b. 1803.
I know the first child sometimes comes early, but that seems excessive!

I believe that there were three brothers, George b. 1795 or 1796, Valentine b. abt 1807, and Christian b. abt. 1800.

Does that sound like the family you are looking for?