SQL to find rows with a similar numeric value

I have a table in a database which lists the similarity of an item to another, where each row(s) is essentially a search result, where similarity is a numeric value.

A row is either a parent (no similarity level) which may have "children" results

Or a child, where a numeric similarity percentage is given of its parent

What I need to do is identify all the items which are similar. This can be done as if two items have a near identical similarity score to a parent, then those two items can be said to be similar.

However; I'm having trouble accomplishing this with SQL. I'm using Access, and can split the table into parents and children if need be, but can't do much more

An example of my table is below:

id, parent, score
aaa,,
aab,,
cas,aab,97
cad,aab,96
agd,aab,70
aac,,
aad,aac,100

In the above example, I'd like to pick out items "cas" and "cad" as the results.

Conversely, I can pick out all the results which are similar to a parent (such as aab and aac) via a simple SELECT query.

Thanks for the help.

via Chebli Mohamed