The whole concept of ‘Family’ tartans didn’t exist before 1822. Before then, people wore what they liked and could afford (some dyes cost a lot more than others) There is some evidence that certain setts (patterns) became associated with certain districts and some VIPs dressed their employees all in the same sett (just for the look of the thing, or for economy’s sake), but that’s it.
If you are a current or former (honourably discharged, otherwise you might risk a beating) member of a Highland Regiment or other entity that has a tartan (such as the USMC), then you are entitled to wear that tartan for the rest of your life. If you come from a ‘regimental family’ but have not served in the regiment yourself, you can probably get away with it.
There are many ‘National’, ‘Provincial’ and ‘District’ tartans which are both attractive and in the Public Domain.