Who Are the Wives of yaacov's sons? Their own twin Sister?

Yes, according to the sages, each of Yaakov's twelve sons was born with a twin sister, and they married them. This was permitted at that time because it was before Matan Torah, before we received the Written Torah at Har Sinai. The laws of forbidden relationships that we have today were not yet in effect. This is similar to how Kayin married his twin sister, and Hevel married his two twin sisters at the very beginning of creation. It was the only way to populate the world at that time, so Hashem permitted it. But after we received the Torah, these laws changed completely, and such marriages became forbidden. Now, some chachamim have a different opinion and say that the tribes didn't marry their sisters but rather married women from other nations. For example, we know that Yehuda married the daughter of a Canaanite. But the dominant opinion among the sages is that each of the shevatim was born with a twin sister and married her. The Torah doesn't explicitly name most of these wives because they weren't as significant to the narrative and the continuation of our mesorah. The women who are mentioned by name in the Torah, like Dina, are mentioned for specific reasons related to important events or lineage.