One of the central ideas of Christianity is the idea of resurrection. You don't have Christianity without it. In Romans, it is the sign that all the charges against Jesus are false (tacit) and that he is Son of God (in the first place, a title meaning Messiah or promised Jewish King, and then in the church, God the Son). In 1 Corinthians 15, it is the sign that our sins are forgiven. Finally, in Romans 8, it is the sign that there will be a general resurrection of the deal and a renewal for all creation.
In Luke 20:27-40, Jesus is debating the resurrection with the Sadducees, who did not believe in a resurrection. Ironically, they accused the Pharisees who did believe in the resurrection of introducing foreign beliefs to Judaism. Ironic because of their own Greco-Romano tendencies.
The trick question was about a woman who was widowed seen times. It was meant to be a reductio ad absurdum argument - indicating that such a situation shows that the idea of the resurrection is absurd.
His reply is surprising on two levels. The second comment is surprising in his use of Scripture - from 'even Moses showed, in the passage about the burning bush, where he calls the Lord the God of Abraham, and the God of Isaac, and the God of Jacob. ' to get 'He is not the God of the dead but of the living; for all live to Him.' All live to God, but how? Are the dead not really lost because they exist is some state, or in the mind of God, or? Christians debate the so-called intermediate state, but orthodoxy affirms the resurrection. Whatever happens in between, the future involves the body.
If you read 1 Corinthians, you see a church rife with sexual issues, either rampant sexual immorality (a man and his step-mother) or abstinence in marriage. Paul condemns both. Yet here in verses 34-36 states that those of the resurrection won't marry because reproduction will be a thing of the past. So what of marriage now?
Jesus makes it clear both marriage and singleness are respectable options, as does Paul in 1 Corinthians. Certainly from a pragmatic point of view, the single person has more time for 'ministry'. In Jewish society, unmarried males were unusual, marriage was the norm. Today many do not marry, but not for these reasons. While sexual urges are not a primary reason for marriage, Paul is quite clear it is better to marry than burn in lust (remember an age of arranged marriages). Not romantic but very sensible. Either married or single - serve God.There is nothing to suggest that marriage now is unspiritual.
But does this describe a dull future? No new people and no marriage? Isn't this really the kind of dualism the Greeks believed in? Well not really, as the future is firmly bodily, and marriage isn't discouraged for this age. Some things serve their purpose for a time - and this casts no shadow backwards on the present. What then happens to marriages in the resurrection? Presumably those relationships, like all others, are transformed into something yet more beautiful?
And what of children? What of the delight of new people, of their wonder and joy for all who see them as they learn about the world? Perhaps we all become more childlike in our wonder, less cynical and jaded, as we explore an eternity with God to enjoy and things to explore. In these things too, we need humility.