Gwen Stefani has cited "irreconcilable differences" in her petition as she seeks to end her 13-year marriage to rocker and actor Gavin Rossdale.

Sources tell TMZ.com Stefani is asking for joint custody of the couple's three sons, Kingston, nine, six-year-old Zuma and one-year-old Apollo.

Rossdale, who has hired divorce lawyer Laura Wasser to represent him, has also filed his response. He is also asking for joint custody.

Reports suggest there's no prenuptial agreement involved and the couple is expected to split their assets.

Gwen and Gavin said in a joint statement: 'While the two of us have come to the mutual decision that we will no longer be partners in marriage, we remain partners in parenthood and are committed to jointly raising our three sons in a happy and healthy environment.'