How do I calculate the centroid point of multiple longitude and latitude data points in BigQuery?

I have a dataset with various longitude and latitude datapoints. I would like to develop a centroid or "average" of those longitude and latitude coordinates in bigquery at a specific level of granularity.

Example of Current Data:

Desired Output (output centroid is made up)

Where the values above are aggregated to a centroid lat and long number.

Consider below

select id, st_union_agg(st_geogpoint(long, lat)) points,
  st_centroid(st_union_agg(st_geogpoint(long, lat))) centroid
from your_table
group by id    

if applied to sample data in your question - output is

which is visualized as