Your grandmother is not sexually attracted to you so while the pheromones may very well arouse her she will be looking for grandpa not you. So if there is a do not disturb sign hanging on the door just tell good old gramps “your welcome” later. 
In most cases family member do notice something different about you but its because normally change in the natural pheromone sig happens over time so they get used to it gradually. When you use synthetic pheromones they dont have that adjustment time so it can be a shock when Moms sweet son comes home giving off a red hot sexual vibe. In most cases moms will not like it till they get used to it.
There is more about this subject in the studies and abstracts section.
Mark had some good observations.
Tisha