Hello there and thank you for your question! I was diagnosed with osteopenia, the precursor for osteoporosis, awhile back and have done a ton of reading on hip fractures and brittle bones, etc., so this question is very interesting to me. I'm very sorry that your relative is having to go through this. What alison b wrote above is right on in terms of how the hip fractures often happen. We think of older people as falling and breaking their hips, but in reality the hip often breaks, and then they fall. And much of the time, it is due to a condition like what alysiak mentioned above, like osteoporosis.
I'm not sure that there is a typical treatment as such, because so much will depend on the age, overall health, etc., of the person. In two cases that I know of where the women with broken hips were already into their early 80s when it happened, they were in the hospital for a short time and then transferred to a facility where they could be cared for and do physical therapy. Both women are doing great now.
I hope your relative has a speedy recovery and that they can figure out the cause behind it and help make sure it does not happen again. Best of health to you both, Michelle