My sons room on the second floor is colder than the rest. It is on the southwest corner and is the furthest from the furnace. I have hot water baseboard heat which is warm to the touch. His windows actually have some ice build up on the inside. House is 14 years old.
Corners are more difficult to heat since they have two outside walls. They should have more baseboard length to compensate.
In the short term, plastic window film kits would be highly advised as a quick fix for windows icing up on the inside. Run the tape on the side (and top, and bottom) of the window frame next to the wall and wrap the film all the way over the frame, then heat shrink and trim. Window replacement might well be on the menu, but that's next summer, not today. Film you can do today.
If, as is common, there is only one loop (circulator and thermostat control) for the heat, or one loop per floor, you need to work to balance the heat delivery. The circulator pumps warm water around until the place where the thermostat is gets to temperature. For rooms that are not where the thermostat is, adjustments may need to be made to the "flaps" on the baseboard that control air-flow (and thus heat delivery) to adjust relative heat delivery. Thus, you may need to close (partially or fully) flaps in some "warm enough" rooms to get enough heat into the "too cold" room with its flaps fully open, so that heat delivery near the thermostat is less, and the system runs longer to deliver heat to the colder room(s) before heating the thermostat to the point of shutting off.
You might also want to check for air bleed valves and make sure that there are not trapped air bubbles, which can reduce water flow rate significantly.
While a 14 year old house should be adequately insulated, that's worth checking and considering retrofit for as well. It should have adequate windows, too.
Well whoever has designed the system should have taken into acount the extra exposed outside wall and compensated for it with extra baseboard heating. The most obvious answer however is if you feel the temperature of his baseboard heating and you find that it's cooler than the rest in the house, chances are that there is air trapped in his baseboard heating. If you search around, since I'm unsure if it's cast iron or fin type convection heat. There will be a small air bleeder valve on the furthest end away from the inlet. It's just a small air vent with a little wheel and small outlet just over 1/16" turn it counter clockwise until there is only water coming out without any air mixed with it. This should take care of your son's cool room! Use a thick cloth or small jar to catch the water/air mixture and do it more than once leaving an hour or so in between each time you try. Good Luck.