So in the Winterverse, Winter is not very good at hiding her feelings, such as every time she sees Autumn Spice, she stutters, blushes, and her eye gleams literally form small hearts. Okay, maybe not that last one but you get the idea!
 
Also, I realize that Blueblood and Cadence are technically cousins, BUT Cadence is adopted and spent most of her childhood not as part of the royal family and I don’t consider Blueblood to actually be Celestia’s nephew. I consider him to be a distant relative that is referred to as a nephew because it’s the closest they could get. Also, Winter is adopted.
 
So if they are in any way related, they would be at least twice-adopted second cousins three times removed