Will I see my dead ancestors again?

The Bible is clear that only by faith in Jesus Christ may someone enter into Heaven:

Acts 4:11 “He is the stone which was rejected by you, the builders, but which became the chief corner stone.
Acts 4:12 “And there is salvation in no one else; for there is no other name under heaven that has been given among men by which we must be saved.” 

1Cor. 3:11 For no man can lay a foundation other than the one which is laid, which is Jesus Christ. 

1Tim. 2:5 For there is one God, and one mediator also between God and men, the man Christ Jesus, 
1Tim. 2:6 who gave Himself as a ransom for all, the testimony given at the proper time. 

John 6:53  So Jesus said to them, “Truly, truly, I say to you, unless you eat the flesh of the Son of Man and drink His blood, you have no life in yourselves.
John 6:54 “He who eats My flesh and drinks My blood has eternal life, and I will raise him up on the last day.
John 6:55 “For My flesh is true food, and My blood is true drink.
John 6:56 “He who eats My flesh and drinks My blood abides in Me, and I in him.

John 8:24 “Therefore I said to you that you will die in your sins; for unless you believe that I am He, you will die in your sins.”

John 14:6  Jesus  said to him, “I am the way, and the truth, and the life; no one comes to the Father but through Me.

Therefore, if someone dies without confessing faith in Jesus Christ, nothing can save them from eternal judgment. This is the testimony of the Bible, and we must not compromise on this truth. If this truth is unacceptable to a person or even leads them to reject the salvation offered by Christ, then there is no other option for them. They too will perish:

Heb. 2:3 how will we escape if we neglect so great a salvation? After it was at the first spoken through the Lord, it was confirmed to us by those who heard, 

While we may wish we could see our unbelieving relatives, we will never know them again. Instead, we will receive a new eternal family which are all believers united by faith into one family:

Mark 10:29 Jesus said, “Truly I say to you, there is no one who has left house or brothers or sisters or mother or father or children or farms, for My sake and for the gospel’s sake,
Mark 10:30 but that he will receive a hundred times as much now in the present age, houses and brothers and sisters and mothers and children and farms, along with persecutions; and in the age to come, eternal life.

Scripture quotations taken from the (NASB®) New American Standard Bible®, Copyright © 1995, 2020 by The Lockman Foundation. Used by permission. All rights reserved. www.lockman.org