“Are propositions 60 and 90 the ones that let people who inherit property from a parent or grandparent keep the low property tax assessment?”
It’s not propositions 60 and 90. Those allow people 55 or older to transfer their Proposition 13 tax assessment to a new home under certain conditions.
You’re thinking of California Propositions 58 and 193.
In general, Proposition 58 states that real estate transfers, from parent to child or child to parent, can be excluded from reassessment. In other words, you can keep the same tax assessment.
Proposition 193 expands this tax relief to include transfers from grandparent(s) to grandchild(ren).
IMPORTANT NOTE: There’s a lot more to this than space allows me to explain here. So be sure to read this link to see all the rules and exceptions.