Frisk is a 25 year old woman, when she was a child she fell down in the Underground filled with monsters, tho since this is a true pacifist Frisk, she spared every single monster and then the barrier shattered and all monsters were free, now monsters live on the surface and Frisk does live aswell, then years later, she grew up as she got adjusted to everything, she finds peace with all humans and monsters, her mother is a Goat lady Toriel Dreemur, her brother is Asriel who is also a goat, and her sister is Chara (who got revived) and just like Frisk she is also a human, and her father is Asgore Dreemur who is a Goat aswell