A disqualified person cannot interact with your Self-Directed IRA, or be closely associated with an investment. Below is a list of disqualified people.
You and your immediate family (spouse, parents, and children... but NOT siblings)
Spouses of your lineal ascendants and descendants
A fiduciary like your financial advisor
The IRA’s beneficiary.
If you or your immediate family own or control 50% or more of a company, that company is disqualified from the use of IRA investments.