Insexting

Sexting is the act of sending sensual, risque, or sexual text messages to someone with the purpose of hoping to invoke sexual relations. Insexting is when two people who are related are sexting. It is a play on the words "incest" (because the two people are related) and "sexting" (because it is the act of sexting).
I myself have been discovered insexting my mom.

Guy talking to a group of several friends: "Hey everyone, guess what? I solved the mystery of that girl Ted has been texting all the time".
One person in the group: "You mean sexting instead of texting. I know he was sexting to some woman, he said so."
Guy talking to a group of several friends: "I read the messages. It is sexting, but the woman he was texting is his mother, so technically he has been insexting."
Group: "Haha Ted has been insexting his mom, hahaha. That is absolutely wild."