Rhea Perlman, actress ("Cheers") and wife of actor Danny DeVito ("Ruthless People" and the upcoming "Throw Mama from the Train"), has given birth to a seven-pound, 11-ounce boy, said a spokesman for Cedars-Sinai Medical Center. The son, named Jake Daniel Sebastian DeVito, is the couple's first boy and third child. . . . Pop singer Kenny Loggins and his wife Eva also had a recent addition, a baby girl named Isabella--a name Loggins used in a song recorded for a coming LP. Both Eva Loggins and Isabella are resting at Loggins' house in Santa Barbara.