Brian Henson as Kermit

From Muppet Wiki

After the death of Jim Henson, many reports claimed that Jim's son, Brian Henson, would be the one carrying on the character of Kermit the Frog, incorrectly assuming this because Brian had puppeteering experience.

Many people still hold the incorrect sentimental notion that Jim Henson's son took over the role after his father's death. However, it is veteran Muppet Performer Steve Whitmire who took over the role of Kermit in 1990.