When you added that to the strong bond between Naruto, who intended to become Konoha’s Hokage, and Gaara, Suna’s present Kazekage, that easily made the bond between Suna and Konoha the strongest amongst all the villages united under the Union. With such external forces at work as well, it was natural that Shikamaru and Temari had reached a stage of existence where both was the other’s biggest support within the Union.