How do I build on my super if I choose to reduce/quit my job?

Q.

How do I build on my super if I choose to reduce/quit my job due to lifestyle choices i.e. offspring or looking after parents? Would I need to invest my partner's money from his job or even borrow money to increase the amount of money needed for our retirement?

The key to building wealth is to invest using funds you have generated from or create a pool of investment by using excess income to borrow. Unfortunately if you are reducing your income the wealth building process becomes much more difficult as you are reducing the amount of resources available. In your situation I think you should start from scratch and consult a financial advisor to discuss exactly when you would like to retire and how much you believe you will need then. The advisor can then help you design some strategies that are appropriate for your goals and these could include borrowing for investment or salary sacrifice.