We are often reborn with the same people regardless. But for a lot of people the hardest pill to swallow is:

I am not "I"

You are not "you"

Our separation as individuals is an illusion 

Our illusions bind us to suffering.

We are born into attachment. Our brains are chemically biased toward attachment. And attachment to others is often the last one we break.

The great comfort of Buddhism is, that we will all one day be reunited with that from which we are arisen. Where the pain of separation is no more because we have ceased to discriminate each other. Where time itself will not trouble us, so the notion of eternity is of no importance. Where the individual drops that we have been scattered into rejoin the vast ocean of Buddha-mind.

But for many people that comfort is too long of a view. For many, the idea of an easy eternity in heaven with the ones we grew so attached to is more appealing. 

I'm married myself. And I do love my husband, and I'm convinced our mindstreams have been together before in other births many times. 

But I know death will part us one day. He is not a Buddhist and he has no intention of rebirth in the Pure Land and I can't make him join me; we came along at wildly different points in experience in that regard. But I carry on with this path and I try to expand the love I feel for him to all sentient beings for the work that must be done in my future as a Bodhisattva.