Just another perspective: I know two elderly women who were married to men 20 and 25 years older than them. Both of them said to me, after the deaths of their husbands, that they had loved them, but had they known what it would be like, they never would have married them - and both warned me not to marry someone much older.
In both cases, these women were the carers for their husbands: in one case, the husband developed dementia (which now affects 1 in 3 people) and in the other, he was a creaking gate who eventually died from a stroke. They were loving, kind and couldn't have done more for their husbands, but inevitably, it takes a toll. Both of them developed new leases of life after the deaths of their husbands, and became much "younger" in their outlook and attitudes etc and had some happy years of widowhood before dying themselves.
So- age gaps do work, and when you love someone, you care for them, no matter what happens: you don't give up on them, no matter how hard things get, out of respect for your shared history etc However there is a massive difference between someone who is 60 and someone who is 85, both in terms of abilities and outlook. Of course, people die at 60, and blah blah blah - but there is a very real possibility you will spend a considerable amount of time caring for your elderly husband at the same time as caring for your elderly parents, perhaps, at a time when you had hoped to be enjoying the freedom of retirement.
Do what feels right for you - but accept that age gaps aren't as straightforward as people sometimes present them.