There is no cut-and-dry answer to your question. It depends on your nature, the nature of each sibling and your individual relationship with each one of them.
Before I explain further, please allow me to make the following observation: I read your question and sense your concern, but please do not worry. With the meteoric rise in the number of people who are turning to a Torah observant way of life, this isn’t the “issue” it once was. In fact you have an opportunity to grow even closer with your family and increase family harmony despite differences. The guiding rule of Judaism is, “All its ways are pleasant and all its paths are peaceful (Proverbs 3:17).”
“Do not avoid your responsibility toward your relatives” said the prophet Isaiah (58:7). The Talmud interprets this verse to mean that there is a special responsibility upon each family member toward the other members of his family (Ketuvot 52b). For example, this special responsibility manifests itself in Judaism’s laws of charity, where one is obligated to aid one’s own family before financially helping anyone else. The Talmud also states that one should “draw his relatives close” in explanation of the phrase in Psalm 15, “He did not tolerate the shame of his relatives (Maccot 24a).”
These classical Jewish sources express universal human instincts and emotions in this type of a situation. Relationships between siblings are often complex, especially when one is undergoing a drastic change in life style, and enthusiastic attempts to get a sibling to join in and draw closer to the Torah are usually counterproductive.
Therefore, if a sibling shows interest in Judaism, the ba’al teshuva is clearly obligated to offer any assistance and explanation he can. If not interest is shown, however, it is preferable to leave that sibling alone.
A mere two decades ago it was rare that a person would become a ba’al teshuva and make a change to some degree in their way of life. I recall many instances then of family frictions due to seeing the change as unusual and therefore not truly understanding one another. This could be unpleasant. Nowadays, however, it is quite commonplace and frequent that a family member (or even an entire family) becomes more observant in Judaism. People accept each other and speak freely and pleasantly about virtually all aspects of religious practice and beliefs – and all family members grow in their understanding, appreciation and love for their families, whatever paths the individuals choose.
