Walking past 633 Union Street, you may not notice anything’s amiss at first. But if you step back and take another look, you may notice that the building is off-kilter. A closer inspection also shows mismatched brickwork that curves slightly inward on the right side. An awning on the front of the building identifies it as the Leaning Brownstone. Despite its name, the building is not a brownstone, as it is not a townhouse made of brown sandstone nor was it built during the period they were popular in New York….