Proper rehabilitation of the soft tissues of the ankle after a sprain can help recovery and decrease risk of re-injury, but strengthening your bones will take more.
Increasing your bone strength is critical to reducing your fracture risk. Weight bearing exercise, calcium, and vitamin D have been shown to slow the normal bone loss that occurs with aging. In the face of multiple fractures, it may be appropriate to ask your doctor if you should schedule a bone density test. If your bones are less dense then they should be for your age, a prescription medication to improve bone strength may be indicated to reduce your risk of a fracture.
If your ankle is weak from multiple injuries, a high top shoe, such as a hiking boot, will give your ankle more support.
I recommend that you visit your podiatrist for a comprehensive ankle examination that may include diagnostic studies such as and x-ray and MRI to ensure that no surgical intervention is indicated. That way you can be sure to receive the best treatment for your ankle so that you can enjoy an active, healthy lifestyle. Be well.