Pretty close to being spot on, OTC markets doesnt "belong" to FINRA, it is however Regulated specifically by FINRA. OTC Markets is a public company owned and operated by OTC Markets Group Inc., trades under the ticker OTCM on the OTCQX tier.
There is no link between FINRA and the DTCC, the DTCC is a Federal Reserve Board Member and a Registered Clearing House. So it answers to the Federal Reserve as a "bank" and it answers to the SEC as a "clearing house".