Detailed Answer

Short answer: To show you are next of kin and to be appointed administrator of a reopened estate in Delaware you will generally need a certified death certificate, certified documentary proof of your family relationship to the decedent (birth, marriage, adoption, or divorce records as appropriate), a sworn affidavit or petition identifying heirs, any prior probate paperwork for the estate, and any required waivers, notices, or bond paperwork. You must file a petition with the appropriate Register of Wills or court and serve interested parties. Delaware’s probate and intestacy rules are in the Delaware Code (Title 12) and under the Delaware Courts’ Register of Wills procedures.

What “proving next of kin” means in practice

“Next of kin” means the person or persons who inherit under Delaware’s intestacy rules when someone dies without a valid will. Who qualifies as next of kin depends on the family relationships recognized by Delaware law (spouse, children, parents, siblings, etc.). To be appointed administrator you must show you are an heir with a priority claim under those rules and that no one with priority objects or already holds valid appointment.

Delaware statutes governing intestate succession and appointment of personal representatives are located in Title 12 of the Delaware Code. See the Delaware Code (Title 12) for statutory language: https://delcode.delaware.gov/title12/. For practical filing and county procedures see the Register of Wills pages on Delaware Courts: https://courts.delaware.gov/register-of-wills/.

Common documents you will be asked to provide

Certified death certificate for the decedent (official government copy).
Proof of relationship showing how you relate to the decedent. Examples:
- Birth certificate listing the decedent as parent (for children).
- Marriage certificate (for a surviving spouse).
- Adoption decree (for adopted children).
- Divorce decree or death certificate of an intervening spouse if relevant.
Certified copies of any will or letters previously issued (if the estate was opened and closed earlier). These show what happened in the prior administration and whether the estate was fully distributed or closed administratively.
Affidavit(s) of heirship or sworn statements from other family members confirming family relationships if primary documents are unavailable. Courts accept these where documentary records are lacking, but they carry less weight than official certificates.
File-stamped petition to reopen the estate (or application) and proposed order requesting appointment as administrator. The petition must identify the decedent, state why reopening is required, list known heirs, and indicate who previously served (if anyone).
Proof of notice or service to other heirs and interested persons — the Register of Wills or court will require that you notify all parties with an interest under Title 12.
Bond or surety documentation if the court or Register of Wills requires a fiduciary bond for an administrator in your case.
Tax or accounting records if the prior administration had accounting or unresolved tax matters; these documents help the court decide whether reopening is appropriate.

Typical procedure to be appointed administrator when an estate is reopened

Gather certified documents proving identity and relationship (see list above).
Prepare and file a petition to reopen the estate and to appoint a personal representative with the appropriate county Register of Wills (or court if required). The petition explains why the estate must be reopened (e.g., later-discovered assets, mistake in distribution, missing heirs).
Provide proof of service or notice to all interested parties and post any required public notices.
If there are no priority objections, the Register of Wills will issue Letters of Administration (or the court will sign an order) after any bond requirement is met.
Once appointed, the administrator receives formal authority (letters) to act for the estate and must follow fiduciary duties, file inventories/accountings, and distribute assets under Delaware law.

Hypothetical example

Suppose Alice died intestate in New Castle County. The estate was opened and closed by a distant cousin years ago, but later funds from a forgotten bank account are discovered. Bob is Alice’s adult child and now seeks appointment to reopen the estate and collect the assets. Bob would file a petition with the Register of Wills, include Alice’s certified death certificate, his birth certificate showing Alice as his mother, any prior letters from the old administration, an affidavit identifying other heirs, proof of service to those heirs, and obtain any required bond. If everything is in order and no higher-priority heir objects, the Register of Wills may issue Letters of Administration to Bob so he can handle the newly discovered assets.

Where to file and who to contact

Delaware’s probate matters are handled locally by the Register of Wills in each county. Procedures and required forms vary slightly by county. Start with the Delaware Courts’ Register of Wills information page for county contacts and procedural guidance: https://courts.delaware.gov/register-of-wills/. For statutory rules on intestacy and fiduciary duties see Title 12, Delaware Code: https://delcode.delaware.gov/title12/.

When you should talk to an attorney

Consult an attorney when heirs dispute priority, when the estate has complex assets (business interests, out-of-state property), when significant tax or creditor claims exist, or when the prior administration’s records are inadequate. An attorney can prepare the reopening petition, represent you at hearings, and ensure you meet notice and bond requirements.

Helpful Hints

Request certified copies of vital records early — obtaining certified birth, marriage, or death certificates can take time.
Collect original or certified documents rather than photocopies; courts and registers usually require certified copies.
Prepare a clear family tree and timeline to show how you connect to the decedent.
If primary documents are unavailable, gather secondary evidence (affidavits, baptismal records, school records) and explain the efforts you made to obtain primary records.
Give timely written notice to all likely heirs; failing to notify an interested party can delay reopening or cause the court to deny your petition.
Ask the Register of Wills which bond amounts or forms they currently require; bond rules vary by case size and county practice.
Keep copies of every filing and certified receipt of service — you will need proof you followed procedure.
If the estate was previously closed, obtain the prior estate file or docket entry to see why it closed and what must be undone to reopen it.

Disclaimer: This is general educational information about Delaware probate procedure, not legal advice. I am not a lawyer. For advice tailored to your facts, contact a Delaware probate attorney or the local Register of Wills.