At last, New Kids on the Block are getting back together. A person involved in planning the long-rumored reunion told us yesterday that the mega-selling boy band will make their comeback official with an announcement Friday on the “Today” show. According to our source, all five original New Kids – Joey McIntyre, Donnie Wahlberg, Danny Wood, and Jordan and Jonathan Knight – have committed to the reunion, which comes on the 20th anniversary of the Boston band’s biggest-selling LP, “Hangin’ Tough.” A tour is planned, the details of which will be announced soon on the group’s newly redesigned website nkotb.com. Before breaking up in 1994, NKOTB was a worldwide phenomenon, selling more than 50 million albums. The band members, now all in their mid- to late-30s, have hardly been idle since. McIntyre continues to record, tour, and dance – he was on “Dancing With the Stars” – Wahlberg has appeared in several films; Jonathan Knight is a developer in the Boston area; Jordan Knight still records and made a regrettable appearance on “The Surreal life”; and Wood is a music producer.