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It depends on your database. I assume you have some functionality provided by it, some API or something you use to fetch and send things? Well, use whatever it is that fetches information to do so,...

You want function (method) arguments:
public InitializeIndividual( int anId, string aFirstName, string aLastName, string anExistingRelation, ... )
{
id = anId;
name = aFirstName;...