Not having seen the full will(s) either,
I'd be thinking that if they were a testamentary gift
direct to you (plural) from your grandmother,
without passing through your Mum's hands in any capacity (eg as a trustee),
then they may not be part of your Mum's estate.
I mention this because sometimes, people use the term "trust',
when that's not what's actually happening.*
I also note that you said "in our names" - which make me wonder
about them actually being a direct gift, back when.
If it turns out that they are (and always have been)
yours (as they say) "free and clear", then I'm
hard pressed to see them as part of your mother's estate.
Why this matters is twofold.
- if they are actually yours, then your other relatives
probably have no claim on them (even if they
might have a family provision claim on other assets); and
- they might be capital gains tax exempt,
because of how long ago it was (before CGT existed in Australia).
One further thing - if it looks like
@Paul Cott and I are disagreeing here,
we're actually not.
We're coming at the question from two different angles,
and neither of us feels that we have enough information
to make a firm call on it in this case.
One last thing - if you get any grief, ask your trustee mother
to account for 40 years of missing dividends...
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* ..while noting that it doesn't take much for a trust to arise.
Even if your Mum "looked after them for us while we were little",
that can be enough for a thing called a "constructive trust".