At least one household in a support bubble must be a single-adult household (living alone). This means that if you live alone, you can form a support bubble with two parents. Alternatively, if one of your parents lives alone then you can form a support bubble with them, irrelevant of the size of your own household.
If you are in a support bubble then you do not need to maintain social distancing with the other household. You cannot change your support bubble, or see people from outside the support bubble unless you are socially distanced. For more details, you can read the Government Guidelines to Support Bubbles.