Oh Baby! Chris Martin's Girlfriend Jennifer Lawrence Has A BIG Baby Secret — Does He Know?

As Jennifer Lawrence and Chris Martin's romance heats up and the Oscar-winning actress gets used to life as a possible stepmom, RadarOnline.com has learned that she's already getting some practice changing diapers. That's because the 24-year-old recently added another role to her list of accolades – aunt!

JLaw's big brother Blaine Lawrence and his wife Carson welcomed a baby boy named Theodore in September.

The Hunger Games star stunned on the April 2014 cover of Martha Stewart Weddings as a bridesmaid in their October 2013 nuptials – and since then, the happy couple has kept the baby news under wraps … until now.

According to friends and family, Jennifer's six-month old nephew was expected to be born in late September in the Lawrence family's hometown of Louisville, Kentucky.

When she's not filming, all the babysitting practice will come in handy when it comes to her on-again/off-again relationship with Gwyneth Paltrow's rocker ex-hubby. After a brief cooling off period, they spent Easter weekend together in NYC and Boston. The Coldplay frontman is a father to Apple, 10, and Moses, 8, with Paltrow.