Hi @Marklin and welcome to Reach Out... You ask a very good question. It is a tricky topic as every teen is different in regards to their maturity, which includes their physical, mental and emotional maturity and every family and expectations are different.
I believe that it would be ok to talk with your sons girlfriends parents about the sleep over arrangements and any concerns that you may have. You will feel more at ease if you know everyone is comfortable with the sleeping arrangements. When I gave my daughter permission to first sleep at her boyfriends house for the first time, she told us that they were ok with it, however his parents had no idea she was staying over. Her boyfriend was suppose to seek permission, but didn't... awkward!! You also want to make sure that your son is staying in an environment that is safe and that he will be properly cared for, so I feel it would be ok to ask.
The legal age for consensual sex varies across Australia (16-17 years) so depending on what state you live in and the age of your sons girlfriend, legally they could be doing nothing wrong, but is is still hard as a parent to navigate this time. Reach Out has some good resources about sex and teens Click here and Click here
I didn't know my daughter was sexually active until after the fact. I wish I had known before hand so I could have better prepared her, but I don't think she stopped to consider what advice her mum might have at the time!! I have always told my daughter to be safe, make sure it is consensual and nobody does anything they are not comfortable doing. We have a pretty open relationship so I am fairly confident she follows this advice.
I think you have to do what you feel it is right. Remember that teens don't need a night sleep over to be sexually active, and it is better to be safe than sorry. All the best on what ever you decide, I am sure you will make the right decision for you and your son.
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