Real estate developer Thomas O'Brien is the latest candidate to join the race to be Boston's next mayor, sources tell NewsCenter 5. He is the head of HYM Investment Group, which is behind several big Boston projects, including One Congress, Suffolk Downs and Boston Landing.According to the HYM website, O'Brien is a graduate of Brown University and Suffolk University Law School. He also serves on the boards of several organizations, including The Anti-Defamation League of New England, The Pine Street Inn and The Rose Kennedy Greenway Conservancy.O'Brien's campaign announcement is expected next week.Mayor Michelle Wu, the incumbent, is also expected to kick off her official reelection campaign early next month. Wu, 40, was first elected to the Boston City Council in November 2013, becoming the first Asian American woman to serve on the council. She was unanimously chosen by her colleagues to serve as president of the city council in January 2016, becoming the first woman of color to serve as council president — a role she held for two years.The Harvard College and Harvard Law School graduate was elected mayor in November 2021 and took the oath of office a few days later, instead of the usual transition in January, because she was replacing an interim mayor.Josh Kraft, son of New England Patriots owner and billionaire businessman Robert Kraft, is also in the race. He spent 30 years with the Boys & Girls Clubs of Boston, led his family's philanthropy and has served on the boards of several local organizations.Kraft has critiqued the cost of Wu's legal preparation for her congressional testimony, the White Stadium project, recent bike lane projects and North End outdoor dining restrictions.