TMZ broke the story ... Melissa filed for dissolution of their domestic partnership. In Melissa's docs, she filed for joint legal and physical custody.
But now, Tammy has thrown down the gauntlet, asking for full legal and physical custody. Tammy carried the twins to term, after being impregnated by an anonymous sperm donor.
Tammy, just like Melissa, says in her docs irreconcilable differences as the reason to end their partnership.
Tammy is also asking for spousal support.
Last thing ... it looks like Tammy made a mistake. She filed a dissolution of marriage rather than a dissolution of domestic partnership. The two did not qualify to marry during the time that they established their union.