Brendan Lambert is a main character on ABC family comedy Step by Step. He is portrayed by Josh Byrne.

Brendan is the youngest of Frank's three children, who is portrayed as a shy, carefree youngster, and one of the most accepting of his new family. Brendan appeared less and less as the show progressed, especially after Lilly was introduced in the season four episode "A Foster/Lambert Production". When the show moved from ABC to CBS, the character was written out of the series; the series' producers later admitted in a TV Guide interview that despite his absence, the Lamberts would still refer to their "seven children", making Brendan an unseen character for the final season. Actor Josh Byrne appeared on television series Who's The Boss? and The Family Man.[1] He portrays the younger version of Billy Crystal's character in Mr. Saturday Night, which also features Jason Marsden, who later appears in later run of the series.