Reese Witherspoon with daughter Ava, son Deacon, and her father John on a family hike in the Santa Monica Mountains on May 19, 2012. Credit: AKM-GSI

An open-air hike with the family does a world of good.

On Sunday, five-months pregnant Reese Witherspoon was snapped hiking in the Santa Monica Mountains with her kids Ava, 12, and Deacon, 8, and her father John Witherspoon.

Expecting her first child with second husband Jim Toth, the Oscar-winning actress, 36, recently returned from Nashville, Tenn., to attend a May 11 hearing with dad John, 70, and mom Betty -- who are currently at odds over John's January wedding to Patricia "Tricianne" Taylor. Asserting that John (from whom she separated in 1996 but never divorced) suffers from early-onset dementia, Betty, 63, filed a suit alleging that he committed bigamy, and requested conservatorship over John.

While Betty's whereabouts are unknown, retired ear, nose and throat doctor John is now staying with his famous daughter at the L.A. home she shares with husband Toth, 42.

"Reese is devastated," a source tells Us Weekly. "She wants her mom protected and her dad to get help."