Help with summer vacation babysitting job

So I am in highschool and every summer my family and I go to our cottage for summer break. There is another family from our hometown that also has a cottage a few streets down. Every summer I will babysit their youngest daughter. She is very easy to take care of and the family is great. She has older siblings specifically an older brother who I go to highschool with. He was my first crush but he only ever wants to talk to me during the summer. The other sibling are in college and are not at cottage. Sometimes he will try to hang out while im babysitting. I know he usually will watch his sister but while im here in summer I think they like me just because im another girl and there daughter is mostly around boys as she has all older brothers...

So last night they asked me to babysit got there around 6 they were going to eat with friends. The babysitting was eas she is very fun to hang out with. Her older brother who I go to highschool with was being a bit obnoxious though. Being flirtatious and it was making me uncomfortable so around 9 I told him I was taking his sister to bed. His parents called and said they would be out late and I could go home after I put their daughter to bed or I could stay. I ended up staying. Their daughter went to sleep and I stayed up doing some summer reading. The parents cane home at about 1 am. Well I guess the older brother who I go to highschool with had fallen asleep on the couch. All I hear is his mom start yelling, they definitely had been drinking, to their son to wake up right now! His mom just saying he had to be kidding her that he ruined their couch. Her son just said im sorry he just fell asleep. Then his mom kinda put my confusion at rest and said thats why he's supposed to put his pull ups on before 9 pm! I couldn't believe what i was hearing! He told his mom to be quiet and apologized again said he forgot and it won't happen again. His mom told him just go to bed and assured him she will make sure it wont happen again. Then reminded him to put his pull ups on.

After a few minutes she came in to check on her daughter and realized I was still there. She was mortified asking how much I heard and so worried about embarrassing her son she thought I left. I told her no dont worry I barely heard a thing and I understood. She paid me I left saw a towel on the couch and im sure her son heard me leaving. How can I keep things professional going forward with this family knowing this now about their son who is my age? I was shocked at first but im sure it is embarrassing for him what should I say to their mom next time she asks me to babysit? Should I tell his mom next time I dont mind making sure their son has his pull ups on by 9 so an accident wont happen again like last night?