Doesn't have to be the same manufacturer.
But don't make the same mistake as I did. I have two different manufactures and the height of both cards is different. That made my hardline build a lot harder and I had to just stick a soft tube between the two. If you don't intend on doing hardline setup, then it doesn't matter much.
But before you buy, check the warranty, BIOS settings (I heard that Asus is limiting voltage on their new Strix cards), etc. Stuff that might be important to you.