1. Subtly trying to find out if a family member is dtf without destroying your relationship if they are not.

2. Portmanteau of Incest and Instigate. Putting two or more people who are related in naughty situations to see if they'll go for eachother.
1. John: Dude that girl Annie was all over your dick, why didn't you tap that?
Bobby: She's my cousin! There's no way shes into me, besides her mom would kill us!
John: I think it's time for an incestigation. Be a more flirty, maybe take a walk together.

Annie: Ugh... I flirted with my cousin Bobby to get him to buy us beer and now he's being all weird and gross.
Rita: You went too far girl, he thought you were serious!

Annie: You're right this has all the signs of an incestigating. I gotta reject him ASAP!

2. John: Man I'm so pissed at Bobby for ruining my chances I'm going to incestigate him and Annie just to fuck with him.
by NedryOS May 22, 2018
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