The couple of 11 years announced their split on Monday

By Karen Mizoguchi
Updated September 26, 2016 02:15 PM
Alessandra Benedetti/Corbis via Getty

Naomi Watts and Liev Schreiber announced their separation on Monday after 11 years together.

Because the couple never married, the division of their financial assets and custody of their children can potentially become “way more complicated” if Watts, 47, and Schreiber, 48, did not have written and/or oral agreements prior to the break up, family law attorney Steve Mindel tells PEOPLE.

“When people are married and get divorced, the rules are pretty clear, but when an unmarried couple splits after a long period of time, it’s like the Wild West, anything is possible,” Mindel explains to PEOPLE.

The Australian actress and Ray Donovan actor – parents to sons Sasha Schreiber, 8, and Samuel Kai Schreiber, 7 – announced their split in a joint statement. “Over the past few months we’ve come to the conclusion that the best way forward for us as a family is to separate as a couple. It is with great love, respect, and friendship in our hearts that we look forward to raising our children together and exploring this new phase of our relationship.”

For nearly a decade, the former couple shared a Manhattan duplex apartment, which was recently featured in Architectural Digest. Designed by Ariel Ashe and Reinaldo Leandro of the firm Ashe + Leandro, it took a total of 10 months for the entire the 19th century inspired home to come to life. According to Leandro, Watts “brought a great eye and taste to the project,” which mimicked a modern take on vintage décor staples by incorporating graphic details such as black-and-white tiles in the kitchen, while still staying true to the retro feel by adding in chairs and art from that era. Watts and Schreiber also recently purchased a $5.4 million Hamptons home together in August.

Unmarried couples who are living together can have cohabitation agreements that can legally protect their rights as a couple in addition to their individual assets if they break up.

If Watts and Schreiber have no such legal document, they can make their own parenting agreements regarding child support, custody, and visitation issues on their own or with a family law counselor.

In the case that court proceedings come into play, a partner can ask for monthly payments of palimony or may request a palimony settlement of a one-time payment. However, a custody or visitation agreement – even one ordered by a judge – is not permanently binding and can be altered if necessary.

RELATED VIDEO: Liev Schreiber and Naomi Watts Talk ‘The Bleeder’

Watts and Schreiber began dating in 2005 after meeting at the Metropolitan Museum of Art’s annual costume ball. The former couple will star in the upcoming boxing film Bleeder that will be released in spring 2017.