I have read that Rav Kook considered Theodor Herzl to be Messiah ben Joseph. However, other Orthodox Jews consider Herzl to be of the Erev Rav, not halachically Jewish, and therefore a Troublemaker. Does Rav Kook’s belief about Herzl being Messiah ben Joseph prevail in Israel only? Also what do the Haredi think of Herzl?? And, are Herzl’s children buried in Israel?? Or did they immigrate to the US and simply disappear from history?? Does Theodor Herzl have living descendants in Israel?

This is a very famous and blatant misquote common in the Haredi community. Rav Kook said explicitly, based upon sources of the Vilna Gaon, that anyone who participates in the ingathering of the exiles, and the physical development of the Land of Israel and Y’rushalayim, has a spark (!) of Mashiach ben Yosef in him, and there are many who fit into that category, including Herzl. Although many haredim don’t feel that Herzl contributed positively to Jewish history, I strongly suggest you open the books and research the issue to decide for yourself! Only demagogues might say that Herzl wasn’t halachically Jewish (just like the Satmar rebbe says that I, and all religious Zionists, are not Jewish!), but were Herzl or I to give a dime to a Jewish woman and say: “May you be betrothed to me…”, believe me the Satmar rebbe would agree that yes, we are Jewish, that woman is now a married woman, and definitely needs a gett (kosher divorce) to marry someone else! Another important point that's crystal clear, is that Zionism brought Herzl, an assimilated Jew, closer, not further, to his people and to tradition, as it has done for most Jews over the last century. Unfortunately, Herzl’s children, as is often the case with orphans (they lost their mother as well, 3 years after their father’s tragic death, when they were aged 11-14), all suffered from mental illness and died tragic deaths, also at a young age, the youngest being killed in the Holocaust. He has no living descendants anywhere. This is irrelevant to your previous question, and has nothing to do with Herzl himself, but for the fact that often those who dedicate their lives to Am Yisrael, their family life often suffers as a result, as is unfortunately frequently seen among the children of famous rabbis and community leaders.