The clothing does not need to be the same but it is important that it complements each other. Some people like matching clothing which is a great idea. However, anything that goes well together should be fine. Just try to avoid people dressed in extremely formal and casual manner at the same time.
It is also important to figure what sort of setting is in place for the portrait. If it is taken in a studio setting with formal furniture, formal clothing will look great. Similarly, if the picture is being taken in an outdoor setting such as a park, casual wear will just be fine.
Avoid Large Prints
It is best not to wear large prints since they can draw more attention than one would like. Wearing relatively plain clothing will keep the focus on the people, which is most important.
Try and avoid light colours since they can generally affect the overall look of the picture. It is best that slightly darker colours are worn which can work with most kinds of backgrounds.
Clothes should be ironed
The clothes worn in the picture should be clean and properly ironed before the picture is taken. This will give a great look to the picture as opposed to wrinkled and dirty clothes which take the charm away from the family portrait.
Shoes should also be as per the clothing. You simply cannot wear snickers underneath a tie and jacket as it will look totally out of place. Similarly, if you are planning of changing clothes for various pictures, it is best that you have shoes matching with the clothes.
The best and brightest thing to wear is your smile. Nothing will make the picture look more fantastic, than your smile .