Finding a reduction for two-Subset sum problem
There is a trivial reduction from Partition to your problem: given an instance $S$ of partition, construct the instance $(S,\frac{1}{2} \sum_{i \in S} i)$ of your problem. This shows that if you take any reduction from Subset-Sum to Partition, you immediately get a reduction from Subset-Sum to your problem. You can find the reduction from Subset-Sum to Partition in many places, or come up with it on your own.