Kärt was born in 1739. Kärt's father was Toots and her mother was Epp. Her paternal grandfather was Peeter and her paternal grandmother is <Unknown>; her maternal grandparents were Peeter and Eva. She had four brothers and four sisters, named Toomas, Paap, Peep, Mikk, Katri, Annika, Mai and Katri. Peep, Kärt and Annika were triplets. She had a half-brother and five half-sisters, named Tõnn, Liis, Tiiu, Mai, Kärt and Ann.