I think there's more to your sibling's taxes than property taxes. The data tell the opposite story - WI property taxes are higher than TX ones, at least if we look at the medians:
https://www.propertytax101.org/propertytaxbystate
As someone living in Fort Worth and making good money as a Staff SWE, I got a tax refund this year. It was due to paying interest on my house, but still.
I'd recommend asking your sibling see if they qualify for the homestead exemption, it's significant. You or they can check if they're using it and see their exact property taxes here:
Texas property tax rates are some of the highest in the country. Should be higher than Wisconsin.
The difference here is really more of an indicator of property values in the respective areas. In major metros in Texas, you're looking at ~2%+ tax rates, which is infact higher than Wisconsin, even in the metros there.
> As someone living in Fort Worth and making good money as a Staff SWE, I got a tax refund this year. It was due to paying interest on my house, but still.
If you paid more in property taxes, that would indicate you can take a larger federal tax deduction... so, if anything, a tax refund implies you paid a lot in local property tax. Either that, or a boatload in interest (or, both). Neither is indicative of local property tax being low.