Hello Sonia,
The Fire service and insurance assessors criticise the use of supply splitters where the splitter its self is not overload protected, even if the supply is. So the use of splitters litters is frowned on.
I'm not sure if the replies above have answered the "If we're sharing the electric does that mean we have to half the ampage fpr use?"part of your question.
The answer to this part of the question is no, you do not simply have half the available amps, but technically you have to say that your combined current needs must not exceed the sites supply.
Say for example the site has a 10A limit (16A is the maximum it can be), you may use 9A and your parents 1A - combined is 10A or any combination provide the sum does not exceed the sites capacity.
If you both were to limit yourself to only half the supply that would be fine, and would avoid nuisance tripping. This will need you to fully understand the current draw of each appliance and to be quite choosey about which ones to use and when.
At least providing the sites supply is compliant with the wiring regulations, even if you did unintentionally try to draw more than the sites capacity, the MCB in the sites bollard should trip and protect the EHU's from damage due to an overload, though as stated at the top of my reply it is not a recommended arrangmant.