Some time back I was asked some very personal questions about heaven. A young boy asked about a schoolmate who died. What if he lived a long time and then died. How would he recognize his friend when he got to heaven? The very next day the question was put the other way. A mother, now advanced in years, talked about the child she lost in infancy many years ago. How would she recognize her daughter in heaven?
The Bible does not tell us everything we would like to know about life after death. That lack of information does not lie in any reticence on God's part, but rather with our own inability to understand the answer. Heaven by definition is a realm unlike the world in which we live. God could tell us everything we wanted to know but the answers wouldn't make sense to us. It's like trying to explain the color green to a blind man. Heaven will make perfect sense to us once we get there.
So the Bible doesn't directly tell us how we will recognize each other in heaven. But I think there are hints that tell us that we will indeed know each other (and all the redeemed) for that matter. I Corinthians 13:12 says that Today we see each other dimly. Our vision is blocked by our human limitations. In heaven, the imperfections of age, sickness, weakness, disease and disaster will all be removed. So will the taint and mark of sin. The result will be that those in heaven, while retaining the essential core of their personality, will shed all marks of human weakness.
Will we know each other in heaven? Yes, of course. How else could it be heaven if we wandered throughout eternity not recognizing those we have loved in this life? We will be the same, yet strangely and wonderfully different, transformed by the grace of God.
One other small hint helps us. When Jesus was transfigured, Moses and Elijah appeared with him on the mountain. That's amazing, considering Moses died and Elijah was taken directly to heaven hundreds of years earlier. But James, Peter and John immediately recognized them.
That brings me to the answer. In the same way that a mother recognizes her daughter's cry in a crowded room, even so we will recognize our loved ones although we have been separated for dozens of years. Age will not matter. The passage of time will not matter. The young boy will recognize his schoolmate and it will be as if he last saw her yesterday. The mother will know her daughter and the daughter will know her mother.
How that could be is a mystery to me. I would not understand the answer if the Lord himself explained it to me. But I believe with all my heart that it is true.