Here are 15 things that might cause your family to fight over your will

As the old gag goes "money isn't everything, but it sure keeps the kids in touch".

It seems so simple. You make a will, you die and any wealth you didn't spend gets split between your family, friends and charities as you see fit.

Yet the word "inheritance" is loaded with emotion, because you decide who wins and loses.

In New Zealand it's also filled with legal uncertainty, thanks to a system that in practice doesn't offer the full "testamentary freedom" that we assume (the ability to leave our money to whoever we like).

"Forced heirship" isn't a feature of Kiwi law either. This is common in European countries. In Scotland there is legal equality for all children. In France "la reserve" means only part of your estate is yours to give away as you see fit. If you have one child, you lose control of half your wealth and, with three children, three-quarters enters la reserve.

While the New Zealand courts only deal with a few hundred cases a year of wills being challenged, don't be fooled. It's so costly people settle out of court. Heirs are forced to make concessions you probably never intended.

Whose fault is that? Greedy adult children? Wicked step-parents? Siblings with years of pent up frustration towards each other?

No, not generally. Most behaviour can be traced back to our own lack of communication with family. Frank discussions eliminate surprises.

If you don't feel the concept of equal sharing works in your family, leave a statement of wishes to help children or the courts understand your thinking. If there was a relationship breakdown with a child, a signed and witnessed letter explaining the history may prevent challenges as it can be used in evidence.

Some New Zealand lawyers now advise clients to leave 10 per cent to children they prefer to disinherit. This is because judges have slowly reinterpreted the 1955 Family Protection Act. The Act was designed to ensure a destitute adult wasn't a burden on the state if family money became available. These days it's crept towards a moral duty to recognise a child's place in a family.

While you can certainly split your money unequally between children, completely disinheriting does risk a judge allocating them a small share.

The hole in your estate from legal fees and years of wrangling can cause even greater financial pain to your intended heirs.

Unequal division and lack of communication won't usually lead to a legal challenge. Yet it does risk a family making concessions to avoid legal costs. People end up sore, surprised, or ruining what were once good relationships, because no one understands what drove your decisions.

At this point, your legacy isn't about money. It becomes tainted with family division and friction long after you've gone.

How can you guess if your tribe will end up having fisty-cuffs over your home, business, or the remains of your KiwiSaver fund?

The risk-factors for an inheritance fight:

1. A second marriage with children and step-children. Sibling relationships divide into camps if surprises arise.

2. Late marriage. While the billionaire and Anna-Nicole Smith spring to mind, it doesn't have to be that racy to cause ill feeling.

3. An age-gap marriage. There is a risk of not inheriting for a long period of time and adult children may try to challenge this.

4. Estrangement of adult children. They could cause legal costs and delays in getting money. It may be lower risk to give them a nominal amount like 10 per cent.

5. An adult child involved in your business, especially if they haven't bought into the business with a market-level arrangement over time.

6. Sibling rivalry where tension quietly simmers. Your will could become a source of friction if your decisions are never explained.

7. Adult children who no longer speak, although their relationship with you may be fine. Being very clear about your wishes could counter their tendency to make life difficult for each other.

8. An adult child with alcohol, drug, mental health or gambling issues. Be very wary of the trouble they can cause if you fail to provide for them. Or the reverse if you over-provide. Good legal advice can ensure drip-inheritances.

9. Adult children with domineering partners.

10. Success disparity between your children. Different work ethics or life-choices make one a saver and the other a spender. It can give rise to expectations where one adult child believes the other doesn't need your money.

11. An adult child who can't maintain financial independence from you may expect additional allowances in your will. If it's not clear which way you are leaning, your legacy could breed resentment between siblings.

12. If your financial gifts haven't been equitable there could be an assumption it will be rebalanced in your will. Have you communicated whether it will or wont be aligned? Have you allowed for the time value of money?

13. Has caregiving and responsibility fallen on one child? They could be single, live locally or just more orientated to helping you. Consider if this will impact relationships after you've gone?. Should it be recognised or ignored?

14. '"Charity shock" in a will. A large donation that appears random to your family can feel emotionally piercing. Having evidence of previous donations or volunteer work can help stop a challenge, but open communication is better.

15. If you're the type to make promises to other people in return for help or services and you've not documented these in your will, don't assume you're off the hook. It can be challenged if there are witnesses or evidence to corroborate their claims. Your heirs will have to use your money to fight off a legal challenge.

Janine Starks is a financial commentator with expertise in banking, personal finance and funds management. Opinions in this column represent her personal views. They are general in nature and are not a recommendation, opinion or guidance to any individuals in relation to acquiring or disposing of a financial product. Readers should not rely on these opinions and should always seek specific independent financial advice appropriate to their own individual circumstances.