Are you noticeably more tired though because you’ve aged 3 years, or because you’ve had 2 kids and are running around after them?
i was noticeably more tired when my kids were in primary school and I was working, keeping on to of the house, school runs etc.
now one is at uni and one doing a’levels I am much less tired as I am working, doing half the housework, no having to get up to get them ready and breakfasted and drop them at childcare/school before doing a full days work, picking them up, feed, bedtime, tidy/clean the house, go to bed, repeat. Now I get up, work, come home, gym, relaxing dinner, maybe chuck a wash on.
two of my grandparents died before I was born. My kids only had 3 grandparents before they were born. Nothing to do with age, just circumstance.