Rav Schwartz has no more connection with the Bilvavi website than Rav Kanievsky ztz"l did with all the websites that post videos & quotes of him.
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Here is some biographical information on Rav Itamar Schwartz (copied from here: bilvavi.net/back-issues/eng/Bilvavi_234_Shemini_Taking%20Shelter_5782.pdf):
The Rav attended the Pachad Yitzhak Yeshiva of Rav Yonasan David, Shlit"a and graduated from the Ponovitch Yeshiva of Rav Gershon Edelstein, Shlit"a.
The earliest of more than 50 sefarim of the Rav where enthusiastically endorsed by Rav Gamliel Rabinovitch, Shlit"a, Rav Moshe Sternbuch, Shlit"a, Rav Yitzchak Zilberstein, Shlit"a, the Tolna Rebbe, Shlit"a, Rav Moshe Mordechai Karp, Shlit"a, amongst others.
Using an eclectic approach, the Rav's teachings speak to the hearts of Jews from all walks of life.