There are not 'two ends' of marriage

Using Benedict XVI's hermeneutic of worship one could stumble upon a new articulation of matrimony.

Jettison the terminology of 'two ends', which are obfuscatory (as Dietrich von Hildebrand said) and inadequate to describe marriage.

There is one end to any sacrament: worship, union with God.

Sex is the liturgy of the sacrament of matrimony.

It is the act of worship.

Therefore we look for its 'work', its 'opus'.

For the Mass, it is the re-presentation of Calvary.

For Matrimony it is the re-presentation of Genesis, the creation of the image of God.

The fruit of the Mass is communion with Jesus, in which is the fruit of the communion of believers.

The fruit of Matrimony is the community of spouses.

So there is ONE end: union with God

This is achieved through the the liturgy/opus/work of representing Genesis, i.e. begetting a baby.

The fruit of this work is the community of spouses.

Baptism would be the representation, too, of Calvary in which the creation of the new image of God is present in the baby.