you don't need to take classes or get a peice of paper to be a professional level masseuse.
Heck, there is a nun in our area who goes to the local minor league baseball staduim whenever there are games and gives massages, and never was professionally trained. Heck, she goes to colleges and teaches people how to give non-sexual massages.
So, taking the fact that this adult male may be quite knowledgable on massages, it is very reasonable that he'd give them to his family...just like a professional masseuse might.
The key is if he is massaging their buttocks, inner thighs, or breasts.
outer/lower thighs, midleg, calf, foot, face, shoulder arm, neck, back, forearm, hand, etc those are all legitemate massages that are 99.9% of the time non-sexual.