SEC FORM 3

SEC FORM 3SEC Form 3

FORM 3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person^*

Sites Eric

(Last)

(First)

(Middle)

470 PARK AVE S

8TH FLOOR SOUTH

(Street)

NEW YORK

10016

(City)

(State)

(Zip)

UNITED STATES

(Country)

2. Date of Event Requiring Statement (Month/Day/Year)
04/24/2026

3. Issuer Name and Ticker or Trading Symbol
MIAMI INTERNATIONAL HOLDINGS, INC. [ MIAX ]

3a. Foreign Trading Symbol

5. If Amendment, Date of Original Filed (Month/Day/Year)

4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director	10% Owner
	Officer (give title below)	Other (specify below)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Beneficially Owned
1. Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
1. Title of Derivative Security (Instr. 4)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	4. Conversion or Exercise Price of Derivative Security	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
Nonqualified Stock Option (Right to Buy)⁽¹⁾	08/01/2021	03/26/2030	Miami International Holdings Inc	7,500	$16.14	D⁽²⁾⁽³⁾
Nonqualified Stock Option (Right to Buy)⁽¹⁾	07/01/2022	03/26/2030	Miami International Holdings Inc	7,500	$25.98	D⁽²⁾⁽³⁾
Nonqualified Stock Option (Right to Buy)⁽¹⁾	03/27/2023	03/26/2030	Miami International Holdings Inc	9,554	$19.84	D⁽²⁾⁽³⁾
Nonqualified Stock Option (Right to Buy)⁽¹⁾	04/01/2024	03/26/2030	Miami International Holdings Inc	9,174	$20	D⁽²⁾⁽³⁾

Explanation of Responses:

1. These options are fully vested.

2. On April 24, 2026, Eric Sites, who serves as a Managing Director of Horizon Kinetics Asset Management LLC (HKAM), was elected to the Board of Directors of the Issuer. Mr. Sites does not exercise investment discretion on behalf of HKAM with respect to the securities of the Issuer.

3. On April 28, 2026, HKAM filed an amendment to its Schedule 13D wherein it reported beneficial ownership of 11,162,809 shares.

	/s/Jay Kesslen, attorney-in-fact	04/28/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 5 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
* Form 3: SEC 1473 (03-26)

SEC Form 3 filed by new insider Sites Eric