oyakodon

https://en.wikipedia.org/wiki/Oyakodon

Japanese term for when the parent and child are in a threesome with the same partner, typically mother and daughter. The third partner is not related by blood, this tag is not used for general family group sex.

Oyakodon (親子丼), literally "parent-and-child donburi", is a donburi, or Japanese rice bowl dish, in which chicken, egg, sliced scallion (or sometimes regular onions), and other ingredients are all simmered together in a kind of soup that is made with soy sauce and stock, and then served on top of a large bowl of rice. The name of the dish is a poetic reflection of the fact that both chicken and egg are used in the dish.

Chicken - Parent
Egg - Child
On rice - On the same partner

Use this when there's a threesome involving mother_and_daughter_(lore)