Your question did not specify what solvent they were soluble in, so I assume that it is water. The only answer that I can give (and it is a general one at that) is that these are both examples of carbohydrates, and they both contain hydroxyl groups (which is an -OH group) in their structures. Hydroxyl groups are typically polar, and thus would enhance the polarity of the overall sugar molecule, making it soluble in a polar solvent, such as water (the saying in biology and chemistry is “like dissolves like” so “polar dissolves polar”). There are exceptions to that rule, but it is what is generally observed.

I hope that makes sense and helps you. Let me know if I can be of further help. [email protected]