Womanising?

or don't want to get pregnant

or don't want to get pregnant

Hence the 'uncommited'

Or when one person in the relationship has an incurable STI (e.g. HIV) and doesn't want to pass it on to their partner.

Hence the "insecure"
I've never heard of anyone sleeping with someone that they know has a disease/infection.

Just because you haven't heard of it doesn't mean it doesn't/shouldn't happen.

So you're telling me there are humans who willing have sexual intercourse with someone, whom they know have an std without any use of contraceptive?

As far as I'm concerned, ALL extramarital relations are, by definition, open. If you don't want to be cheated on, then get married. Otherwise, there are no rules to say who you can and can't have sex with. Again, unless you are married. It's the norm, everyone does it. It just surprises me how shocked and upset people get over it. And if the girl or man doesn't like it - break up! That's the beauty of relationships, unlike marriage, they're so fluid and dynamic, there are no commitments or rules, no boundaries or requirements. Anything goes.
And my ex girlfriend did exactly that, she was having sex with half a dozen other men. Was I shocked or surprised? Absolutely not (was a little annoyed that she kept denying it after getting caught red handed lol). Because I did the same thing as well and will continue to do the same in any future relationship. It's really not a big deal. People always have the option to break up if they don't like it. There's no way I'm going to stay loyal to just one woman, unless she was Kate Beckinsale when she was in her 20s lol.

lol

Hate the fact boys are socialised to be so delicate and sensitive to girls, and put them on this pedestal of moral authority. They are not angels, and most of them will take advantage of your kindness.

They will say "real men treat women with respect" or "real men put their women above all else", but then they end up going for the guys who do exactly the opposite of what they say. They want guys who do and say whatever the hell they want, when they want, not some simpering puppy that treats them like a goddess for having a vagina.

Why are you trying to avoid becoming a womaniser? It's a good thing, you should embrace it. Become like Charlie Harper. Your brother isn't doing anything wrong or bad. It's not considered cheating if you're not married, just because you have a girlfriend doesn't mean you can't have sex with other women. If she doesn't like it or accept it then break up, very simple. You can still treat them well at the same time, it's fine.