Thanks for your question.
Yes, there is and it is called a declaration of trust. It is a deed signed by the registered proprietors of the property (presumably both your parents) and it would state that upon sale of the property you would receive an agreed proportion for the proceeds of sale to take account of your help in financing the purchase.
It could be registered against the property as a notice. Both your parent and both of the "we" you refer to would need to sign it as a deed (witnessed).
Any administration of your parent's estate in the event of their passing would have to take account of this deed.
If this is useful please kindly click accept so that I may be rewarded for my time. It will be gratefully received and you will free to ask follow up questions.
DISCLAIMER: Answers from Experts on JustAnswer are not substitutes for the advice of an attorney. JustAnswer is a public forum and questions and responses are not private or confidential or protected by the attorney-client privilege. The Expert above is not your attorney, and the response above is not legal advice. You should not read this response to propose specific action or address specific circumstances, but only to give you a sense of general principles of law that might affect the situation you describe. Application of these general principles to particular circumstances must be done by a lawyer who has spoken with you in confidence, learned all relevant information, and explored various options. Before acting on these general principles, you should hire a lawyer licensed to practice law in the jurisdiction to which your question pertains.
The responses above are from individual Experts, not JustAnswer. The site and services are provided “as is”. To view the verified credential of an Expert, click on the “Verified” symbol in the Expert’s profile. This site is not for emergency questions which should be directed immediately by telephone or in-person to qualified professionals. Please carefully read the Terms of Service (last updated February 8, 2012).