Being the same age does not guarantee there will not be a caregiver relationship

My grandparents are 3 years apart in age. My grandmother has always been a bit of a health nut, my grandfather was definitely not. She couldn’t control him obviously, and the lifestyle caught up with him in the predictable ways, so she spent about 15 years doing increasing caregiving until about a year ago when he needed to be go into a facility because he became bed bound after a hip fracture and his dementia was too severe. I’m now convinced a mismatch in lifestyle is more likely to result in a prolonged caregiver role than a mismatch in age.