My mother-in-law married an Australian. Can I immigrate to Australia?

In this case, if you want to immigrate to Australia, you can basically rely on yourself.

Parents can apply for their children to immigrate to Australia, but the condition is/kloc-unmarried children under 0/8 years old or financially dependent on their parents.

But your mother-in-law's Australian status can get extra points when you apply for immigration.

I suggest you see if you can meet the requirements of skilled immigrants in Australia.