Does a photograph of model Karlie Kloss show "Trump's sister-in-law" voting for Joe Biden? Yes, that's true, assuming the Trump referred to is senior adviser to the president Ivanka Trump and not her father, President Donald Trump.
Aww shit it's getting hot. (Trumps sister-in-law).
This is what the post looked like at the time of writing:
(Source: Facebook screenshot taken on Tue Nov 3 20:10:45 2020 UTC)
Kloss is married to Joshua Kushner, brother of Jared Kushner, Ivanka's husband. Jared Kushner is also a senior adviser to President Trump.
That makes Kloss and Ivanka Trump sisters-in-law.
The photograph is not the first time Kloss has made her political preferences known. In a 2016 Instagram post, she revealed that she voted for Democratic presidential nominee Hillary Clinton, who lost to Trump.