If you have GenerateBlocks plugin, you can add a query loop block to add same category posts, but it will require the GenerateBlocks Pro plugin to exclude the current posts from the query loop block.
if you want build them with GenerateBlocks Query Loop, then yes you would need to purchase the Pro version.
With GB Pro, you will be able to set Query Loop Parameters that use the Current Post argument.
For example, show posts that share the same Category terms as the Current Post.