Draw a sample from a dataset with similarities (based on 6 variables) to another already-drawn sample

I have drawn a sample "S1" (around 100 individuals) that I am interested in from a specific dataset.

Now from the same dataset I would like to draw another sample "S2" with individuals which are more or less similar (based on 6 variables) to the individuals from S1.

How could I do such a thing on SPSS? ...or is there any key term for naming what I want to do?