Guardianship of Clyde

The maternal grandparents appeal from a decree of the Probate and Family Court discharging their petition for the guardianship of their minor grandson, Clyde, and awarding the biological father sole legal and physical custody of his son. They contend that (1) the judge erroneously applied the standard to determine parental fitness; and (2) the judge’s findings are clearly erroneous and not supported by the evidence. We affirm.2

1. Background. We summarize the findings of the Probate *768and Family Court judge.3 On May 25, 1990, Clyde’s mother and father were married in Ayer. Clyde, the only child…