is there official ages or birthdays for the characters?
The events of Echo take place during Spring break of 2015 (So likely mid March). I mention this as some people's ages could be affected if they had an early birthday.
Chase is 21 years old, and in the events of Route 65 he is 15 during November 1st, 2008. It is likely Chase has a birthday between Late April and November and was born in 1993. (The wiki says he is 22, but that conflicts with him stating that he is 21 in a few scenes and some stuff Carl says)
Leo is 23 years old, and I believe that there was a scene where it was mentioned that he chose to celebrate Carl's birthday on Wednesday as Carl's is the closest, with Leo's already having passed and been a month prior. If this is correct, Leo was born in either January or February of 1991.
Jenna's age is not stated outright, but when the group was in school together, she was a year above Chase and year below Leo. She is likely 22 or 23 during the events of Echo. I can't make a guess as to what month she was born, but it likely is later in the year and not in March or April and was born in either 1992 or 1993.
TJ, baby of the group, is 19 years old. He is stated to be 2 years younger than Chase and is finishing up his first year of College when the game takes place. This is also brought up in Route 65, where TJ is only 13 years old. He was likely born in 1995, though he could be a 1996 baby instead.
Flynn is the oldest member of the gang and is 25 years old. This is reinforced with the events of Route 65 with Flynn already working with his Aunt and not being in High School, most likely having graduated in 2007. Depending on what month he was born, Flynn was born in either 1990 or 1989.
Carl is the only member who birthday is relatively set, being around late April (stated to be the end of next month, so this assumes the game takes place in mid March). Most likely Carl was born late April of 1993, however there are a few conflicting details. According to the wiki Carl is 21, however, there is a scene where Carl mentions that he cannot legally drink alcohol yet. This also conflicts with Carl being Chase's age, as being 20 would make Carl a year younger than Chase and likely put him in a grade lower. In Route 65, Carl mentions looking forward to driving, which would happen next year if he was 15 in 2008.
MINOR SPOILERS for the next Person
Sydney was shown to be either Chase and Carl's age, or a year younger than them, meaning he was likely born in 1993 or 1994, depending on when his birthday was. While I cannot give you an exact month for his birth, I can give an approximation for his death. In Route 65 it is mentioned by Chase that the group had to go back to school after Sydney's funeral. As they had been swimming in Lake Emma it is likely that Sydney drowned in Early to mid August of 2003. This would also match with the information that his father died 6 months prior on a hunting trip. When we are shown the hunting trip, it is described as a colder time of the year and Sydney and his father have to put on warmer coats. Mr. Bronson likely died in February of 2003.
If I have anything wrong, let me know and I'll fix this post! Also feel free to check the wiki, but beware of spoilers: Echo (Visual Novel) | Echo Project Wiki | Fandom