you can find the marriage. The uncle was Barend Pieter van der Ban. He married in Haarlem in 1921 Helena Anna Bieler.
In an old newspaper from 1928, De Indische Courant, I found that they worked in the former colonie "Indië".
That they were separated in the second worldwar is for sure. The women and children under 16y. were separated from the men. The conditions in those camps was terrible and a lot of them died. A lot of men had also have to work on the building of a railway in Thailand/Siam.