The charming chamber musical “John & Jen” opened in 1995 at the Lamb’s Theatre and is enjoying its twentieth anniversary revival at the Clurman Theatre on Theatre Row. It is a musical montage of the lives of Jen Tracy (Kate Baldwin), her brother John (Conor Ryan) and Jen’s son John also played by Mr. Ryan and explores the sometimes complicated dynamics of family and the family system, particularly the relationships between sister and brother and the often tumultuous relationship between mother and son.

The ten songs in Act I rehearse the lives of Jen and her brother John (born when she was six years old) from his birth (“Welcome to the World”) until his enlistment in the Navy and his death in Vietnam. Although Jen promises to protect her kid brother from life’s difficulties as he “finds his way” including keeping him safe from their father’s abusive behavior, she ultimately leaves home after high school, moves to New York City and becomes enmeshed in the anti-war, anti-establishment culture of the 1970s (“Hold Down the Fort”). Without Jen to protect him, John succumbs to his father’s abusive criticism and does what he can to appease his wrath (“It Took Me a While”).

The twelve songs in Act II chronicle Jen’s life as the mother of her newborn son she names John. This naming has as much to do with remembering her brother as it does to formalize her inability to deal with her brother’s death and to project all of her unresolved bereavement on her unsuspecting son. “Old Clothes,” Christmas II,” and “Little League” are songs that resound with the sorrow of unresolved guilt, the tension of transference, and the deleterious effects of an adolescence without a successful separation-individuation process. The chilling “Just Like You” reverberates with these coming of age trials. In a brilliant reprise of “It Took Me a While,” Ms. Baldwin’s Jen realizes what she has done to her son and with “Graduation” and “The Road Ends Here,” releases John and herself from the past. She is able to admit that she has been too possessive and over protective (“That Was My Way”) admitting that her love was “too strong” and she needed her son “too long.” In the final song “Every Goodbye Is Hello” mother and son are able to start new lives as healthy, separate, and individuated adults.

Ms. Baldwin and Mr. Ryan navigate Andrew Lippa’s music and Tom Greenwald’s lyrics with an honesty and authenticity that reveals the richness of the score and the depth of the lyrics and honors the story of siblings whose complicated yet not uncommon family system leads them in disparate paths and the story of a mother and son who eventually understand the meaning of unconditional and non-judgmental love. Under the careful direction of Keen Company Artistic Director Jonathan Silverstein, Kate Baldwin and Conor Ryan demonstrate successfully what musical theatre ought to be. Their performances are never caricatures: nor do these performances ever become cartoonish. The audience is always aware of the age difference in the characters they portray. Their onstage chemistry is remarkable and believable. Steven C. Kemps’s scenic design and Josh Bradford’s lighting design cleverly dramatize the rough edges and shadowy corners of the human mind as it attempts to navigate the obstacle course called life.

It is a joy to see all that a Broadway performance ought to be played out on the Off-Broadway stage at the Clurman Theatre on Theatre Row. Thanks to a brilliant cast and an inventive creative team, the Keen Company has scored a hit worth seeing.