Much has been written about how brothers and sisters, or parents and children, reencounter each other in subsequent lives. It's very common in past life therapy. If you're going to travel in and out of time, what would be more natural than to develop traveling partners?
What's the most compelling Christian case against reincarnation?
There's just this general cultural habit of thinking salvation has to be worked out in a single lifetime. And yet many of the early Church fathers, such as Origen, believed in reincarnation. It's a habit we can overcome. For most of Christian history, we thought the world in front of us was the same as it was when it emerged from the hand of God. Now we've made the transition to seeing the universe as an evolving universe, and with that a transition from classical theology to process theology. We've had to develop new habits of thinking that are informed by the facts. The Christian has always had a deep commitment to following the facts wherever they go, because their God is not simply a God of history, but of nature too. Whatever is factually true of nature must be compatible with revelation. Christians have always been able to make that transition, even though they may kick and fuss a bit in the beginning.
So you think in 100 years many Christian churches will accept reincarnation?
Absolutely, because the empirical evidence is getting stronger and stronger. They'll come to accept that it's simply a fact of life. Once they make that transition, they'll find there are any number of ways that a Christian can affirm all the fundamental tenets that Christianity holds dear and make it compatible with reincarnation. Just as at first we thought evolution would be incompatible with the Christian faith, but now there are many theologians who have comfortably reconciled the two.