Helping Aging Parents Without a Power of Attorney?

If my younger brother has POA, executor and health advocate powers for my aging parents can I still sell their house (meet with real estate agents, renovate their current home), help them do their banking (pay bills, set up online banking, etc.) and make medical/health decisions for them (pills, home support, shower, meals, shopping)? Or am I limited to helping pack, cleaning, driving, etc.?