Biden was against this rather strongly in 1983 until he’s apparently for it now. Even RBG said 9 was the right number and she was about as liberal as it can get.

https://www.dailymail.co.uk/news/article-9472687/Democrats-preparing-unveil-new-legislation-pack-Supreme-Court-four-new-justices.html

So they want to increase the court to 13.  If this happens the GOP will make it 18 if they take over.

If they pull this off then adding 2 states to the union will be next.

If some of these old justices would simply retire at a time when similar ideologies would replace them things would be easier.  RBG should have retired when Obama was in office.