Just to add to the good comments made above... an understanding of the basic principles of our (admittedly fiendishly complex) income tax laws is important as an investor I think. So too is a basic understanding of the nature and operation of any legal structures like your "family trust".

With respect to tax, the first principle is that there's an allowable deduction for you in relation to interest costs (not principal repayments) on amounts you borrow to buy invesments with the expectation that they will produce an income. For example rent, dividends/trust distributions.

With that basic principle in mind let's look at what you've done. First though let's consider the nature of a family trust.

Typically what people call a "family" trust is structured as a discretionary trust. Assuming that's the case for you, there is no "investment" or piece of it that you buy in contributing money to the trustee of your family trust. Rather, as a beneficiary you'll have a right to be considered by the trustee to receive none, some or all of the net income of the trust and any assets of the trust in the case of the trust coming to an end (again, more complex than that but it'll do for now).

So you have either gifted or loaned the borrowed money to your trustee. If the former then definitely you have not borrowed to buy an income producing asset. If the latter then it may be that some or none of the interest is deductible unless you charge a higher interest margin than you're paying...But of course if you were to do that then one of the tax benefits of borrowing to invest, namely negative gearing, would not be available. (Negative gearing being when expenses exceed income from investments so that the excess deductions which are not offset by the investment income are available to shelter some of the income from your job or other sources.

Clear as mud?

Hope that helps.
Cheers
N.