if your little bro doesn't want to hear it, let him be. let him stay a virgin. your advice will be received way better when he's the one coming up to you in need.
i'll tell my children that there's no such thing as "deserve" or entitlement. people won't necessarily treat you how you feel you should be treated based on your actions and that's ok. you have no control over that. the only thing that matters is power and leverage. the only thing you control is your own actions and reactions. no one owes you p*ssy, a date, a kiss, etc. but at the same time, you don't owe anything to anyone. you have complete control in what situations you choose to be in. if you can't live with the terms, get out of the situation. but if you choose to stay, it's your fault. i'll teach them accountability and teach them to set their own standards and principles. and finally, i'll teach them to reward loyalty. but at the same time, just because someone shows loyalty in a situation, doesn't mean they'll be loyal forever so stay awake and always treat people accordingly.
this advice goes for both sons and daughters.