Both in our 30s. Sibling doesn't work/earn much due to health issues. I (and partner) earn a very good salary. I (we) like spending lots on presents for our parents as we like sharing our good fortune by gifting parents expensive things sometimes for birthdays/Christmas as we can afford it (be it an ipad, an experience type gift or a few hundred pounds for short breaks etc).
However I always feel conscience that this might be make my sibling feel awkward/uncomfortable (they are also my older sibling by a few years which sort of increases the awkwardness). But then not doing so and holding off spending money purely for this reason also feels a bit strange/overthinking. My sibling has never indicated they find it insensitive/awkward etc .. but then they probably wouldn’t even if they did.
Parents are always super happy to receive gifts and have never expressed any awkwardness about situation. And we also spend quite a lot on sibling gifts (but again, always conscious in the back of my mind not to go overboard). Would be interested to hear peoples take on this, especially people in similar family situations.