ACS PUMS OC (Own child) and RC (related child) variables

Does anyone have information on how these variables are set. I thought they would be set based on the child's relationship with the head of household (HH). But I am finding children with RELP = 02 (biological child of HH) and OC = 0 (not the own child of the HH) and RC = 1 (related child of HH). So obviously I have something wrong here. Any help would be appreciated. I am trying to find the parents for all children in the ACS so any other suggestions are welcomed.