In No Regrets, the gang finds out Justin's pregnant at the hospital when he has complications, but they don't know Brian's the father. They find that out - again at the hospital - after Justin gives birth and Jack (a nice Jack) is there handing out "I'm a grandaddy" cigars, lol. No scene like that with Lindsay.

ETA: And then in the sequel she's just bitter and bitchy because Justin's pregnant again (Brian, too!) but Brian still won't give her any sperm.

Not sure about the sequel to the sequel.