[x]

I haven't been able to find anything out about Benjamin Burton, but many people in the Border States were caught between the two parties and didn't really fit into either of them. George Fisher, the Delaware Congressman associated with Benjamin Burton was a Unionist elected on a "People's Party" platform. I suspect there were a lot of left-over Whigs and Know-Nothings who didn't want to support the Democrats but weren't wholly committed to the Republicans.

Francis Preston Blair was a slaveowner from Kentucky who came to oppose the expansion of slavery and left the Democrats for the Free Soilers and then the Republicans. His son Montgomery Blair was in Lincoln's cabinet and his other son Francis Jr. went back and forth from Republican to Democrat. One of the Blairs was involved with one of Sumter Commander Robert Anderson's children (married or not is unclear), and that's where the actor Montgomery Clift came from.

[BroJoeK]

x: "I haven't been able to find anything out about Benjamin Burton, but many people in the Border States were caught between the two parties and didn't really fit into either of them. "

Right, the issue here is whether Dinesh D'Souza is FOS for saying (if he did say, as is claimed here), no Republican own slaves.
So some of our posters have scoured the internet for examples of slave-holding Republicans and they've come up with now four names, Grant, Wallace, Fisher and Burton.
But on closer look it's not clear which actually owned slaves or if they had yet become Republicans when they did.

jeffersondem quotes Julia Grant as saying she owned slaves until Lincoln's Emancipation Proclamation, which would be between mid-1862 and early 1863.
But this narrative says Grant was a Democrat, not becoming Republican until mid-1863.

So I've seen nothing yet which reliably represents a full-blown Republican slave-holder.
D'Souza is not the one FOS.