A lot can contribute to someone having some I call them "episodes" while being on medication. It is different for every individual.
Many factors can contribute. One being, are they on the right combination of meds. It can take people months to years to find just the right combination. I hit the jackpot and i'm very greatful because I take 3 and it was the right combination. Only took me 6 months to become stable. Another factor is are they taking their meds like they should. Another thing to keep in mind is even if a person is stable for months on meds, they will probably need their meds adjusted every so often so it is important that they see their doctor as needed.
From your position, I would say just stay supportive, ask your family member often how they are feeling and be encouraging and remain positive. You sound like a very caring person.
~Lia
crazymusiclvr@aol.com