The city is mourning the death of long-term School Committee member and tireless volunteer Kevin Sullivan, who died suddenly of a heart attack Sunday. Sullivan, 52, a lawyer with Sullivan, Hayes and Quinn, the father of two and brother of two mayors of Westfield, was a long-time advocate for children and an “all-around great guy,” friends said. “I never heard him say a bad word about anybody. I never heard him complain. His family is well-known in Westfield for their community involvement. He also leaves parents Richard Sr. and Edie Sullivan and brothers Mayor Brian Sullivan and former Mayor Richard Sullivan, Bo Sullivan and his sister Janet.