google bigquery – How to count ID occurrences in multiple columns?

I’m trying to figure out how many rows does an ID appears a table, when that ID can be in two columns.

| ID    | ID_GROUP            |
|-------|---------------------|
| 65630 | 62931, 62869, 66045 |
| 62931 | 65630, 62865, 65583 |
| 65583 | 62870, 66045, 62868 |
| 66045 | 67001, 65972, 63156 |
| 62868 | 65630, 62868, 62931 |

Id like it so that the result is:

| ID    | COUNT               |
|-------|---------------------|
| 65630 | 3                   |
| 62931 | 3                   |
| 65583 | 2                   |
| 66045 | 3                   |
| 62868 | 2                   |