From PEOPLE Magazine Click to enlarge
He still takes the stage like the blue-collar bad boy he's always been, but to four little ones back home in Bloomington, Ind., John Mellencamp answers to the name of Papaw.

"I've been a grandfather for so long it's as normal to me as being a man," says Mellencamp, 49. The hard-driving rocker assumed the title at 37 when his then-18-year-old daughter Michelle (from his first marriage to Priscilla Esterline) gave birth to Elexis, now 11—followed by Colin, 6, Hannah, 4, and Grace, 2. "I swear in front of the kids, and playing in a rock band is probably not very grandfatherly," he says.

But while a visit with Mellencamp is no walk in the park, it may be a day in the pool. He had one installed in Michelle's nearby backyard "as a blanket gift" after missing some recent birthdays, he explains. "I'm sure John doesn't fit the bill" of a stereotypical grandfather, says his third wife, model Elaine Irwin, 31, mother of their sons Hud, 6, and Speck, 5. (He also has daughters Teddi Jo, 19, and Justice, 15, from his second marriage to Vicky Granucci.)

Mellencamp doesn't look the part either. A 1994 heart attack forced the 5'7" road rat to curtail touring and smoking and take up running and weight lifting. "I didn't work out at all until I had the heart attack," admits Mellencamp, who has spent most of this year collaborating on a musical with author Stephen King. So has he improved with age? "Anyone can be sexy at 30," says Mellencamp. "But until they turn 40, guys aren't worth a damn anyway."