No it isn't a euphemism for having sex. It can be in our culture but not in Jewish culture.
We sometimes use "living together" as a euphemism for sex but it need not be.
In Jewish culture, unlike our own culture, marriage is in two stages.
The first is called
kiddushin. T
he word "kiddushin" comes from the root Qof-Dalet-Shin, meaning "sanctified." It reflects the sanctity of the marital relation. However, the root word also connotes something that is set aside for a specific (sacred) purpose, and the ritual of kiddushin sets aside the woman to be the wife of a particular man and no other. (Judaism 101). At this point the two are legally married, hence in Mt 1:19 Joseph is descibed as her husband and decides to divorce Mary.
The second stage is called
nusuin and this is when the husband brings the bride into his home. Today the two often take place one after the other but this in Jesus' time, and very often, during the interim period, the husband was busy preparing a home for her.
Something to ponder on.
The Church is described as the bride of Christ. In John 14 Jesus says to the gathered apostles, the Church,
In my Father’s house are many rooms; if it were not so, would I have told you that I go to prepare a place for you? And when I go and prepare a place for you, I will come again and will take you to myself, that where I am you may be also. (John 14:2-3 ).
The Church and Jesus have completed
kiddushin and are awaiting
nusuin which will happen later. We are waiting
The Spirit and the Bride say, “Come.” (John 22:17).