Cast member Bruce Boxleitner holds an Identity Disc as he poses with his wife Melissa Gilbert at the world premiere of the film "TRON: Legacy" in Hollywood, California, December 11, 2010.[Photo/Agencies]

It has been a difficult week in the love lives of TV's Gilbert sisters, with both women enduring breakups of their long-term relationships.

Melissa Gilbert, who became a child star on the long-running television series "Little House on the Prairie," has filed for divorce from her husband, actor Bruce Boxleitner, five months after they announced their separation.

Court papers filed in Los Angeles cited irreconcilable differences, and the two are seeking joint custody of their 15 year-old son, Michael.

Earlier in the week, the 47-year-old actress's younger half-sister, Sara Gilbert of "The Talk," ended her 10-year relationship with Allison Adler, a writer-producer of "Glee." The couple will share custody of their two children, People magazine reported.

Winning the role of Laura Ingalls on the wholesome family drama "Little Prairie" at age 8, Melissa Gilbert later struggled with drug and alcohol dependence, according to her 2009 autobiography, "Prairie Tale." She has appeared in numerous TV movies and infomercials. From 2001 to 2005, she served as president of Hollywood's Screen Actors' Guild.

Sara Gilbert, 36, also began her television career young, becoming a regular cast members of "Roseanne" at 13.

Boxleitner, 61, has credits that include "TRON Legacy" and the television series "Heroes."