First recorded by The Superiors (1987).
Hit version by New Kids on the Block (US #1/UK #2/CAN #1/1990).
https://youtu.be/lMIZR0f8zBM
From the wiki: “‘Step by Step’ was written by Maurice Starr, discoverer of The New Edition (1982) and New Kids on the Block (1984), and was originally recorded by one of Starr’s later group creations, The Superiors. ‘Step by Step’ was released as a Motown single in 1987 with no apparent chart impact.