Dear Rabbi, I have never had a real idea of which Nusach I should Daven. My parents are not that religious and I am growing. My Dad only goes to Shul on shabbat and holidays and my mother is not observant but is Jewish. I do not know the Nusach my grandparents Davened. My brother is a very observant Ashkenaz Jew. I am becoming more religious slowly and I would like to Daven Nusach Sefard not Nusach Ashkenaz or Chabad Nusach Ari. Is it OK to switch? Should I change my Tefillin as well to Sefard style? It also seems like my parents have no Minhagim and my brother is making his own Minhagim. If I switch to nusach sefard what does that mean regarding Minhagim and which ones I follow? These are complicated question I know I just have not really had real answers to them. I am hoping you all can help. Thank you.
There are different opinions on this matter, however if you don't have a decisive Nusach of your father and you wish to change to Nusach Sfard because you feel you will Daven better that way, you can with no doubt change your Nusach Tfilah [Divrei Chaim 2OC 8, Yechave Daat 3:6, Divrei Yatziv Likutim 17] As for your Tefilin, you don't really need to replace them as there are only minor differences if at all. On a different note - if your Tefilin are from your Bar Mitzvah I would seriously consider them be checked by a qualified person as there are good chances they are not Kosher or of very poor Halachic quality.