People generally don't expect to have someone in their family start down a new spiritual path. And so it's only natural for Jews to become fearful when a loved one becomes a follower of Yeshua. (Jesus Christ)
Please allow me to explain why this fear is unwarranted, and how it can be rather easily alleviated.
I think we would all agree that fear itself is often irrational. Everyone experiences fear from time to time, and much of it is not based in fact. Instead, our fears are often rooted in erroneous assumptions. But even when our fear is irrational, it is no less troubling within our soul. When fear grips us, we feel extremely vulnerable and at risk.
Nothing is more sacred to people than their faith and their religion. So when a Jew begins following Yeshua, it feels to the family like the sky is falling. It's natural to assume this development will weaken the family bond, as well as the Jewish presence in the world. May I suggest that such a transition doesn't have to stifle family unity. Nor does it have to lessen the Jewish presence in the world.
In fact, your assumptions about Jewish followers of Yeshua may be all wrong. Most Jews who accept Yeshua as Messiah maintain these qualities:
1) They are just as appreciative of their Jewish heritage as ever, if not more so.
2) They remain just as engaged in their Jewish traditions.
3) They love their fellow Jews at least as much as before, if not more so.
4) They still believe the God of Abraham is the One true God.
5) They continue to love everyone in their family unconditionally.
That last one is absolutely huge. And it speaks volumes as to the authenticity of the spiritual birth which has taken place in the lives of "Messianic Jews." (see John 3:1-21)
Jews who trust Yeshua are just as Jewish as every other Jew. If you doubt that fact, just ask them about it. After all, shouldn't they as Jews be the ones who get to define their own Jewishness? No one can take their Jewish identity from them, and Yeshua certainly isn't attempting to do such a thing.
Try to think about it from their perspective. They had not planned to accept Yeshua as Messiah. But it happened, and now they love Yeshua as the One who fulfilled Isaiah 53. And that's just one of several hundred messianic prophesies which all point specifically to Yeshua. While Messianic Jews will always love Yeshua, please know that their love for you is no less. In fact, it has actually increased. That may be hard for you to grasp right now, but it's true.
Even if you feel like your loved one has chosen Yeshua "over" your family, I urge you to reconsider that assumption. It simply isn't the case. They have chosen to accept Yeshua by faith, but that doesn't mean they have chosen to reject you. Not by a long shot. They love you with a deep and abiding love, and always will. They love you as a cherished family member first and foremost. And if you will maintain that same love and acceptance toward them, your family will be richly blessed with a spirit of unity.
Family unity is essential, even when complete spiritual unity is not currently a reality.
But there is one more solid reason why it is unnecessary to be fearful of a family member following Yeshua. The God of Abraham has always told His people they don't need to be afraid. He is your God. He will watch over you and your family. And if you will trust the God of Abraham to help you accept your family member, then He will do it. He will strengthen you. He will uphold with His righteous right hand. And so you need not fear. (see Isaiah 41:8-10)
After all, "there is no fear in love, but perfect love drives out fear." (1 John 4:18) The perfect love of Yeshua can drive fear out of your heart, and also out of the spiritual and emotional atmosphere surrounding your family. This divine love is a supernatural reality flowing from the God of Abraham.
Please remember this my friend. Most of our fears are irrational. And that is certainly the case in Jewish families where one or more in the family meet Yeshua. But rather than allowing it to weaken your family bond, why not let it strengthen your unconditional love for one another? That choice is within your power. After all, it's fairly easy to love our family members when they agree with us on important issues. It's only when we have different perspectives that our love is really put to the test.
If your family is going through a test right now, I encourage you to stay close to the One who made this promise to Moses: "My Presence will go with you, and I will give you rest." (Exodus 33:14) Seek His Presence. Be open to His plan. And watch Him deliver you from bondage to fear and anxiety.
My wife and I have been married for 24 years. When our 4 children were young, I would often lay my hand on the head of Sarah, Aaron, Hannah, and Jonah, and pray the Aaronic blessing over them individually: "The Lord bless you and keep you; the Lord make His face shine upon you and be gracious unto you. The Lord lift up His countenance upon you, and give you His peace." (Numbers 6:24-26) I have prayed that blessing for our children thousands of times over the years. And I suspect you desire that same blessing for your loved ones.
The God of Abraham will strengthen you my friend in the midst of your family dynamics. He is up to more than you may realize right now. For the place where you are standing is holy ground. (see Exodus 3:1-6)
May God's love for your family produce faith and hope, and may your love for one another produce unity and acceptance.