The 29-year-old, who followed his father into the ring, was found dead on a beach.
His devastated father paid a moving tribute to the sportsman, nicknamed the Lion of Alka, who also participated in mixed martial arts (MMA) after moving to the United Arab Emirates (UAE).
Chris Eubank Snr said: “I never imagined that I would write these words or feel the feeling I now have of the loss of my son.
“My family and I are devastated to learn of Sebastian’s passing days before what would have been his 30th birthday.
“He leaves behind his wife Salma, his son Raheem born just a month ago, his mother Karron Meadows, his brothers Nathanael, Chris, Jr, Joseph, a sister Emily and countless relatives and friends.
“Sebastian grew up in Hove, England, but in recent years he has made his living in Dubai where he had a large circle of friends and was a leader in adopting a healthy lifestyle and alternative therapies.
“Besides being a personal trainer and professional boxer, Sebastian was also a deep thinker who loved to challenge accepted wisdom.
“He was loved and respected by all who knew him and will forever be remembered by his friends and family. As a family, we now kindly ask for space and privacy to celebrate your life and remember the son, brother, husband, friend. “
Karron Meadows added, “Our whole family mourns the tremendous loss of our son and brother, Sebastian. Please respect our grief and our privacy as we try to understand our loss. “
Seb, who was born in Brighton, had a successful amateur career becoming a professional boxer in 2018, winning three professional fights, his last earlier this year.
In April, he posted about his joy at being able to box again in front of a crowd, writing on his Instagram: “Respect to my opponent, he was strong and resilient and came to put everything on the line.
“He was chasing my head, trying to knock me out with brute force, but he didn’t know the legendary Eubank granite chin. “
He then asked his fans if he should choose between MMA or boxing.
Seb, a vegan who wrote poetry while out of the ring, was scheduled to fight on the o2 in his brother Chris’ victory over James DeGale in 2019, but the fight was called off because the event was overflowing.
He said after his successful MMA debut in January of last year: “When I entered the arena, I wanted to fight mixing both MMA and boxing, and compete in different weight divisions, so let’s see where I go next.
“I have been in the United Arab Emirates for four or five years now. I entered MMA thinking I had to train properly. I can’t just win. “