She'd raised five children by herself, and Liz Norden was ready for the empty nest.

Two of her daughters, 24 and 26, still lived with her, but they were barely home and busy with their own lives, so Norden, 51, talkative and cheery, was beginning to have days and nights to do what she liked: spend time with friends, play poker, maybe just relax.

But then a bomb tore through the Boston Marathon, sending torrents of shrapnel through a crowd. Norden's phone rang that day, and she heard her son Paul say, "Ma, I'm hurt real bad."

Boston bombings: An article in the Jan. 12 Section A about families affected by the Boston Marathon bombings said that brothers Paul and J.P. Norden each lost a portion of their left legs. It was their right legs that were injured. —

Paul hovered on the edge of death for days, and the family could not immediately locate another son, J.P., who had just one pint of blood left in his body when he arrived at a hospital. Both brothers lost their left legs: J.P. below the knee, Paul above the knee.

It's obvious that the lives of many of the Boston Marathon bombing victims have been changed forever. J.P. and Paul, both fit men in their 30s, were roofers, and will probably look for a new line of work. What's less obvious is how entire families have been damaged.

Authorities say 264 people were injured in the bombings, and 16 lost limbs. That translates to hundreds, perhaps thousands, of family members and friends whose lives, too, were changed dramatically on April 15. For some caregivers, the changes were temporary, perhaps until a victim completed rehab.

For others, like the Nordens, the challenges continue.

Norden recently moved from a third-story apartment to a ground-floor, three-bedroom unit to accommodate J.P. and Paul, who live with her for the time being. She sleeps on the couch because her youngest daughter is still living with her for now, plus she wants to be able to hear her sons if they call out in the night, which they often do.

Norden, who is separated from her husband and cleans houses for a living, takes her sons to medical appointments, does their laundry, sits nervously through their surgeries. And, in ways she hasn't in years, worries.

"You're constantly worried — God forbid there's a fire in the middle of the night and they don't have their leg. It's just different now," she said. "Paul has gotten up to go to the bathroom in the middle of the night and fallen, and of course he says he calls me and I don't hear him."

J.P., 34, is still using crutches as he learns to use his prosthetic, so she helps him carry things: his plate of food, his laundry, his iPad. The boys, as she calls them, have urinals in their bedrooms at night as they adjust to the difficulty of getting up and attaching a prosthetic; she empties them daily.

The work never seems to end. But it's what mothers do.

"It's never-ending — it's just completely different. You think it ends at night, but no, he wants a drink, so you have to go get it," she said. "Not that I'm complaining — I'm so thankful they're here with us."

It's not just day-to-day activities that change. Relationships evolve too. The strongest member of a family may now have to ask for help; people who once stayed away from relatives now have to assist, whether they like it or not.

"There's a lot of change in the dynamics of family," said Sally Johnson, an outpatient social worker at Spaulding Rehabilitation Hospital in Boston, which worked with many of the marathon victims and their families. "One of the struggles is that there's secondary loss for the family. Their lives are certainly greatly affected as well."

In the Norden family, the four younger children always turned to J.P. for help and advice; as the oldest, born when his mother was 17, he helped raise them all.

"I hate having to ask anybody for anything, whether it be my little brother, my sister, my mother," he said. "My mom doesn't complain — none of them do — but it stinks they have to be around to do all this."