multiple pet companion

Hi, I have been trying to get my sim to complete the friend of the animals aspiration. I have completed the first two milestones and am struggling to complete the third one. My sim has one pet as a cat but is friends with three stray animals, all of which have the full friendship bar filled up. This milestone requires my sim to have two pet companions. My sim is companions with her pet cat but I do not see an option to become companions with the pets she has the max level of friendship with. Are sims able to have multiple companions at a time? Can companions be non-pet animals?