The father of both grooms is named Jan. The grooms are probably brothers, despite the difference in familyname for their mothers. If the standard rules were followed, you expect the first born son to be a Jan, but that seems to be not the case, as Leendert is the oldest mentioned emigrant.
There are more marriages with a groom named Assendorp before 1833, but in different places. Marriages were often in the bride's birthplace.