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 who to call on: Her new beau, Jason Trawick, people.com reports.

“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.”

And it is Trawick’s calming influence over her sons that puts mom Spears — whose two-year marriage to Kevin Federline ended in 2006 — at peace.

“He is absolutely fantastic with the boys,” a Trawick pal enthuses. “When you see him with them, you wouldn’t think for a moment that he wasn’t their dad. He treats the kids like they are his own.”