ElPolloDiablo said:If I remember correctly Rambutan is one of those plants that do not stay true from seed.
The chief problem is if you started with a dioecious cultivar (both female and male flowers on the same tree) you may end up with monoecious plants (either male or female flowers) and that it will take you 4-5 years to find out.
The silver lining is this kind of plants tend to make good rootstock for grafting, so it's an experiment worth doing.
PS: I love Rambutan but I haven't seen it for sale in many years. It seems these days it's all lychee or nothing.