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| <?xml version="1.0" encoding="windows-1252"?> |
| <ownershipDocument> |
| <schemaVersion> X0202 </schemaVersion> |
| <documentType> 4 </documentType> |
| <periodOfReport> 2007-01-30 </periodOfReport> |
| <notSubjectToSection16> 0 </notSubjectToSection16> |
| <issuer> |
| | <issuerCik> 0001060021 </issuerCik> |
| | <issuerName> BlackRock Holdco 2, Inc. </issuerName> |
| | <issuerTradingSymbol> BLK </issuerTradingSymbol> |
| | </issuer> |
| <reportingOwner> |
| | <reportingOwnerId> |
| | | <rptOwnerCik> 0000938766 </rptOwnerCik> |
| | | <rptOwnerName> PNC BANCORP INC/ </rptOwnerName> |
| | | </reportingOwnerId> |
| | <reportingOwnerAddress> |
| | | <rptOwnerStreet1> 222 DELAWARE AVENUE </rptOwnerStreet1> |
| | | <rptOwnerStreet2></rptOwnerStreet2> |
| | | <rptOwnerCity> WILMINGTON </rptOwnerCity> |
| | | <rptOwnerState> DE </rptOwnerState> |
| | | <rptOwnerZipCode> 19801 </rptOwnerZipCode> |
| | | <rptOwnerStateDescription></rptOwnerStateDescription> |
| | | </reportingOwnerAddress> |
| | <reportingOwnerRelationship> |
| | | <isDirector> 0 </isDirector> |
| | | <isOfficer> 0 </isOfficer> |
| | | <isTenPercentOwner> 1 </isTenPercentOwner> |
| | | <isOther> 0 </isOther> |
| | | </reportingOwnerRelationship> |
| | </reportingOwner> |
| <nonDerivativeTable> |
| | <nonDerivativeTransaction> |
| | | <securityTitle> |
| <value> Common Stock </value> |
| </securityTitle> |
| | | <transactionDate> |
| <value> 2007-01-30 </value> |
| </transactionDate> |
| | | <deemedExecutionDate></deemedExecutionDate> |
| | | <transactionCoding> |
| <transactionFormType> 4 </transactionFormType> |
| <transactionCode> J </transactionCode> |
| <equitySwapInvolved> 0 </equitySwapInvolved> |
| <footnoteId id="F1"/> |
| </transactionCoding> |
| | | <transactionTimeliness> |
| <value></value> |
| </transactionTimeliness> |
| | | <transactionAmounts> |
| <transactionShares> |
| <value> 1025578 </value> |
| </transactionShares> |
| <transactionPricePerShare> |
| <value> 0.00 </value> |
| </transactionPricePerShare> |
| <transactionAcquiredDisposedCode> |
| <value> D </value> |
| </transactionAcquiredDisposedCode> |
| </transactionAmounts> |
| | | <postTransactionAmounts> |
| <sharesOwnedFollowingTransaction> |
| <value> 43154922 </value> |
| </sharesOwnedFollowingTransaction> |
| </postTransactionAmounts> |
| | | <ownershipNature> |
| <directOrIndirectOwnership> |
| <value> D </value> |
| </directOrIndirectOwnership> |
| </ownershipNature> |
| | | </nonDerivativeTransaction> |
| | </nonDerivativeTable> |
| <footnotes> |
| | <footnote id="F1"> Aggregate transfer of shares of Common Stock, par value $0.01 per share, of BlackRock, Inc. ("BlackRock Common Stock") to BlackRock, Inc. and to participants in the BlackRock, Inc. 2002 Long-Term Retention and Incentive Plan ("BlackRock LTIP") in connection with the BlackRock LTIP. On September 29, 2006, each share of issued and outstanding BlackRock Class A Common Stock and each share of issued and outstanding Class B Common Stock were converted into one share of BlackRock Common Stock. </footnote> |
| | </footnotes> |
| <remarks></remarks> |
| <ownerSignature> |
| | <signatureName> Maria C. Schaffer, Controller </signatureName> |
| | <signatureDate> 2007-02-01 </signatureDate> |
| | </ownerSignature> |
| </ownershipDocument> |
