It sure sounds like it's bigger than just being "conservative". Even regular cons have a better batting average than 1/10. They either failed as conservative parents or they're racist as hinted by the siblings in their statements.
Many children lean in a different political direction than their parents. This is very common.
As far as I can tell -- 7 of his siblings don't support him, and 2 do support him. His parents support him.
That's gotta make for an awkward Thanksgiving dinner.