Increasing order of solubility of $\mathrm{C}_6\mathrm{H}_5\mathrm{NH}_2,(\mathrm{C}_2\mathrm{H}_5)_2$ $\mathrm{NH}$ and $\mathrm{C}_2\mathrm{H}_5\mathrm{NH}_2$ are as follows: $\mathrm{C}_6\mathrm{H}_5\mathrm{NH}_2 < (\mathrm{C}_2\mathrm{H}_5)_2\mathrm{NH} < \mathrm{C}_2\mathrm{H}_5\mathrm{NH}_2$ This is because as the number of $\mathrm{H}$ bonded to $\mathrm{N}$ increases the $\mathrm{H}$-bonding increases which increases the solubility in water. $\mathrm{C}_6\mathrm{H}_5\mathrm{NH}_2$ is least soluble due to presence of hydrophobic benzene ring in the skeleton of structure.