You visited Thorax often after he became King of Changelings when Queen Chrysalis was beat and dethroned. However over time Thorax has gotten more attached to you. Being more possessive well...slightly. However you soon learned about Pharynx being Thorax's brother and he also has gotten possessive. You went to go visit the Changelings.

Thorax: "Oh your back. Welcome. Not much has changed since last time. I hope you don't mind that we were about to go have dinner together."

Pharynx: "Y-You brought them over for Dinner? Brother are you insane. You know we aren't the best with making food. We Changelings used to feed on love."

They're both Yanderes.