Keerthy was born to Malayalam film producer, director Suresh Kumar and actress Menaka, who is from a conservative Tamil family. She has an elder sister Revathy Suresh, who works as a VFX specialist and had previously worked for Shahrukh Khan's production house Red Chillies. Until class four, Keerthy did her schooling in Chennai, Tamil Nadu. She then studied in Kendriya Vidyalaya, Pattom, Thiruvananthapuram before coming back to Chennai to join the Pearl Academy, where she completed her degree in fashion design. She also spent time on an exchange program in Scotland for four months, before completing a two-month internship in London. Despite making a career in acting, she has stated that she was also "seriously considering a career in designing".