A prenup signed before children arrives is written for two people, not four. When a family grows, many couples quietly assume the agreement still covers everything. In practice, having children can change what a court will accept, what the agreement can legally do, and how a judge weighs competing interests when one parent has spent years out of the workforce.
What a prenup can and cannot say about children
Under the Family Law Act 1975 (Cth), a binding financial agreement (BFA) can deal with property and financial matters between the parties. It cannot bind the court on child support or parenting arrangements. Those issues are governed by Part VII of the Act, and no clause in a prenup can override a child's right to financial support from both parents.
That distinction matters. A couple might draft a BFA that specifies a set payout to one party upon separation. If children are born and the primary carer then spends 10 years out of paid work, a court reviewing the BFA under section 90K can set the agreement aside if enforcing it would cause a party to suffer hardship. Caring responsibilities are one of the clearest paths to that finding.
How courts treat hardship caused by raising children
Section 90K(1)(d) of the Family Law Act allows a court to set aside a BFA if, since the agreement was made, a material change in circumstances has occurred and failing to set aside the agreement would cause hardship to a party or a child of the relationship. The birth of children is exactly the kind of material change the legislation contemplates.
Consider a common scenario. Two professionals sign a prenup before marrying. The agreement says each party keeps their own assets and neither makes a claim on the other's superannuation. Five years later they have two children, one partner steps back from full-time work to care for them, and the relationship breaks down after a decade. The homemaker spouse has far less superannuation and a significantly diminished earning capacity. A court asked to enforce the original BFA would have strong grounds to refuse.
This doesn't mean every prenup with children involved gets thrown out. Courts weigh the circumstances at the time of signing alongside what actually happened. If both parties understood the risks, received independent legal advice, and the financial gap is modest, the BFA may still stand. The outcome depends on specifics, not a blanket rule.
The independent legal advice requirement still applies
For a BFA to be enforceable in Australia, each party must receive independent legal advice before signing. That requirement doesn't change when children are involved, but children do raise the stakes around whether the advice given at the time was adequate. If a lawyer failed to flag the risk that caring responsibilities could expose a party to hardship later, the quality of that advice becomes a live issue in any challenge.
Rockwell Family Law Services provides that independent legal advice and, critically, considers how a client's circumstances might evolve before signing any agreement. Our lawyers walk through scenarios, not just the document in front of you. Understanding what a prenup can and cannot do in Australia before signing protects you against surprises years later.
Reviewing a prenup after children are born
The cleanest solution is to review the BFA when a significant life change occurs, and the birth of a child qualifies. Parties can enter a new BFA that supersedes the original, or they can terminate the existing agreement by written consent and start fresh. Neither option requires going to court, provided both parties cooperate and take separate legal advice.
A review gives you the chance to address things the original agreement ignored. Who bears the cost if one party reduces work hours? How will superannuation contributions be treated if one partner pauses their career? What happens if a second or third child is born? These are practical financial questions, not just legal ones, and a well-drafted BFA can address all of them clearly.
Parents who are separating and holding a BFA signed before children should also consider how child support obligations interact with any lump-sum payment the agreement specifies. Child support is assessed separately under the Child Support (Assessment) Act, and a BFA cannot override it. A large lump sum under the BFA doesn't reduce ongoing child support obligations.
What this means in practice
If you signed a prenup before having children, don't assume it will operate exactly as written. Have it reviewed. If you're about to sign a prenup and children are a possibility, make sure the agreement accounts for that reality from the start. A BFA that ignores the possibility of caring responsibilities is a BFA that may not hold up.
For couples thinking more broadly about what their financial agreement covers, it's worth reading about whether a prenup can cover future assets in Australia, since the birth of children often coincides with significant asset accumulation that wasn't contemplated when the original agreement was signed.
Rockwell Family Law Services works with clients at every stage: before signing, when reviewing an existing BFA, and when circumstances have changed enough to warrant a new one. Getting the agreement right when life changes is not bureaucratic caution. It's how the document stays useful.