Is it ok for a man to shower with his mother?

My boyfriend and I went and stayed at the Ritz Carlton, along with his mother. we had adjoining rooms, no big deal right? well, I went out to the pool area to get some clean towels because as usual, my boyfriend skidded up all the ones in the hotel room. Well, long story short, I come back to the room, and I didn't see my boyfriend. the adjoining door was slightly cracked so I went in, and I see steam coming from the bathroom. Nosey person that I am, I go in the bathroom, only to find my boyfriend showering with his mother! I turned to run away, and he suggested that I join them! I was so shocked I started crying and I scratched the dry patches on my hands until they bled. did I overreact? should I have joined in? I suppose it may save some water, maybe I should have.