Each one of them will have two wives; their marrow could be seen through their flesh [and bones] because of their beauty.
If I have 1 wife on earth where will the second wife come from?
To the best of my knowledge and likewise according to what I made research, individuals who go to the paradise (Jannah) have free choose to have their world wives or not. (Although it is narrated that they (wives) actually would be reformed to the best shapes and … (such as the best edition…), of course it is said for the husbands who are interested in being with their wives…
Based on what are narrated, it can be inferred that the purpose would be related to the Houris (except the world wives … as I mentioned above); however on the other hand, it is narrated that as an reward(s) Hour-al-Ain(s) are going to be for them who have amazing and unbelievable shapes and … (Of course it could be inferred from the narrations that this matter is for the wives too (to have amazing…)
In truth, according to the narrations it is narrated that:
… we will give them Hour-al-Ain for marriage (to get married to them)
You have chosen your world wives if … (by some condition(s) and …). On the other hand, (except the word wives), the purpose of the wives or marriage can be related to the Houris as well. As indeed some related interesting issues, I strongly recommend you to read the following source.