"He took amazing care of Jamie Lynn," a source close to the family tells PEOPLE. "Anything ever went wrong, he always comforted her. He took care of her."
Jamie Lynn and her mother say that Aldridge is the father of the 16-year-old Zoey 101 star's baby.
Aldridge, who is believed to be 18 or 19, has stayed largely out of the Hollywood spotlight, only occasionally accompanying Jamie Lynn to Hollywood events.
He grew up in Liberty, Miss., about 30 miles from the Spears family home base in Kentwood, La., and played high school baseball and football (he's listed in a sports directory as a lean 6'1", 165 lbs).
"Jaime talks about how he really likes Casey because he's a great guy," the Spears family source says. "Lynne really likes him, too. He's a good kid, cares a lot about Jamie Lynn. They both adore Casey."
'He'll Be a Good Father'The pregnancy, a source close to Aldridge says, was a surprise.
"I'm sure it was a shock to him," the source says. "He has all sorts of plans for his future. He wants to start his own business, maybe get a degree and make something of himself."
The source says that Aldridge will take responsibility for his actions.
"He's a stand-up guy, and he will take care of the baby," the source says. "He is not the type to let her deal with it on her own. He will be there in any way he can. ... I know a baby wasn't in his plans for right now, but he'll do what he has to do, and he'll be a good father. He really will."
Reporting by STEVE HELLING and PERNILLA CEDENHEIM