How would I make my custom blocks break when one of them breaks if they are touching

Use the block triggers and make a procedure such that whenever one of them is destroyed, it checks all the blocks touching it to see if they're the right blocks (the procedure templates above the codeblocks tab might be useful for that), and if they are, it destroys them. Since they just got destroyed, they'll also do that procedure and cause the chain reaction you're looking for.