Why are these Triforces there? Doesn't they belong to the famous game named Zelda?
In that game the Triforce got special power. You have to find all three of them and combine them. If you do you can make a wish. Therefore it is kinda sacred.

Than I began my research:

These Triforces on the pictures are family crest. They belong to the Hôjô family. They were really mighty in the past because of controlling the shôgun. After a different family died off they took the their name to get more powerful.

This emblem symbolizes three scales of a dragon. It is said that one member of the Hôjô family (Tokimasa Hôjô) went to a mountain on Enoshima. There he praied for wealth for himself and all of his offspring infront of a dragon. The dragon promised to get the wish real and left by leaving three scales behind.
After that it became the family crest to grant protection.

That's maybe the story behind the Triforce of Zelda. Who knows? But right now I think that there is a connection because of the sacred background.
Come to Japan and find out ypurself :D
Maybe you will meet Link and Princess Zelda ^^
That's the story of the family crest.