Can one smply decide to change family tradition and become Sefardi, or Ashkenazi?
Virtually all poskim agree that one should follow the customs of his ancestors, so as to maintain the unbroken line of Jewish transmission. This would include such things as the way we pray, the minhagim of the holidays, or how long to wait between meat and milk. However, there is such a principle as minhag ha-makom, respecting the local custom, so that if, e.g. one moves to a kibbutz where the residents wait 3 hours, so should the newcomers, regardless of their previous practice. Rav Ovadia Yosef – in a lone opinion that differs from the majority – held that an Ashkenazi could adopt Sefardi practices (but not vice-versa). However, he stresses that this person could not then “pick and choose” which elements of the tradition to observe; he would have to keep not only the leniencies, but also the stringencies (e.g. to rise early for Selichot; eat only glatt meat; follow the stricter laws of bishul akum, etc). Of course, a woman who marries into a different culture than the one in which she grew up holds like her husband, but may – with hubbie’s permission – follow her original customs when at her parents’ home. Rabbi Stewart Weiss