When Britney Spears' two sons, Sean and Jayden, were looking for a pal to splash around with poolside during a recent trip with their mom to Mexico, they knew right who to call on: Her new beau, Jason Trawick.

"Jason was great with the kids and you can tell Britney really trusts him," an eyewitness to the group's three-night getaway at the Tides Zihuatanejo resort in Mexico earlier this month, tells Us. "He would pick up Jayden if he wanted to be held, immediately calming the boy down."
Trawick, 37, described as "a nice guy who doesn't take life too seriously," stood by Spears, 27, during her darkest moments (she was involuntarily committed twice to a psychiatric hospital in 2008 and lost custody of her boys the year before).

"[Jason] seems ready to take on the responsibility of a single mom with two kids," another friend of Trawick's confirms.