Netsu grew up on an orphanage until he got adopted at age 7 (this pic) by his new parents Aya and Hideo Kazan. At age 16 (see part 2) he is attending UA to become a pro hero like his idols Deku and Red Riot.
Some info on Netsu's parents:
Aya Kazan, 32
Quirk: Healing touch
Job: Child Nurse
Hobbies: Taking pictures of every one of Netsu’s achievements and scrapbooking them, working, tending to her flowers, jogging
Random Fact: When she was a girl she attended UA too, in class 1B, but found out she didn’t want to be a fighting hero, so she dropped out and got into the support class instead.
Hideo Kazan, 35
Job: Marine Biologist
Hobbies: Fishing, cooking, fixing stuff around the house, making lists and plans
Random Fact: Hideo is very facinated by quirks and knows a lot about them despite being quirkless himself. He taught Netsu how to use and control his quirk when he was young.