Let's analyze each statement to identify the incorrect one about glucose.

Option A: Glucose remains in multiple isomeric forms in its aqueous solution. This statement is correct. Glucose exists in equilibrium with various isomeric forms in solution, including its linear form and two cyclic forms (alpha and beta anomers) that result from the formation of a hemiacetal bond within the molecule itself. The interconversion between these forms is known as mutarotation.

Option B: Glucose is soluble in water because of having an aldehyde functional group. This statement is incorrect though it might seem partially true at first glance. While the aldehyde group can participate in hydrogen bonding, the primary reason glucose is highly soluble in water is due to its multiple hydroxyl (-OH) groups that can form hydrogen bonds with water molecules. The ability to form numerous hydrogen bonds makes glucose highly water-soluble, not just the presence of an aldehyde group.

Option C: Glucose is an aldohexose. This statement is correct. Glucose is classified as an aldohexose because it contains an aldehyde group (-CHO) on its first carbon and has a total of six carbon atoms, making it a hexose sugar.

Option D: Glucose is one of the monomer units in sucrose. This statement is correct. Sucrose is a disaccharide composed of two monomers: glucose and fructose. Thus, glucose is indeed one of the monomer units in sucrose.

In summary, the incorrect statement about glucose is Option B: Glucose is soluble in water because of having an aldehyde functional group. The primary reason for its solubility in water is the hydroxyl groups' ability to form extensive hydrogen bonding, not solely the presence of an aldehyde functional group.