If you are including your spouse, then generally, you just need to provide a copy of your marriage certificate.
Generally speaking, you need to provide documents that demonstrate that you and your de-facto partner have been living together for at least 6 months prior to the date of lodgement of the visa application.
You will need to provide full abridged birth certificates that state the names of both biological parents.
You can include your adult child who has turned 18, but has not turned 23 (and dependent children of any age with a medically accepted disability). You will need to provide documents demonstrating that your adult child is dependent on the family head or on the spouse or de facto partner of the family head. Financial dependency is the only consideration (as oppose to emotional or other forms of dependency).
Custody may be an issue if one of the biological parents is not included in the application. If you want to include your child and your child’s other biological parent is not included, you’ll need to provide evidence to show that you have legal custody over your child and that you have the right to bring your child to Australia. The Department will generally require you to provide legal/government or Court documentation which confirms your custody rights.
You should also upload a complete Form 1221 for each child included in your visa application.
You will need to provide a certificate or letter from your health insurance provider which confirms that yourself and your family members have the required health insurance coverage.