Will there be sex after the Last Judgment?
There will be male and female, but there will be no sexuality the way we know it. This is because at the end of time, our body will resurrect and be reattached to our soul. This is done so we are fully human (body and soul) to stand judgment and to live the rest of our life that way as God had originally designed before the fall.
We will get a glorious body the way Jesus did at his resurrection.1 It is a different body than the one we had before. For example, we will be able to go through closed doors the way Christ did. (If we got our former body, it would just be a resuscitation, not a resurrection.) Since our bodies will be different, so too will sexuality be different. On earth it expresses love and is used to procreate. However, when we are in union with God, we will no longer need sexuality to express love for it is also transformed into a different and higher state of union. The lesson we can get from this is to view sexuality on earth as a foreshadowing of an immense union we will have with God and others after the Last Judgment.
11 Corinthians 15:43, CCC 997, 999