I could be expressing an unpopular opinion (and I may be speaking out-of-turn since I am not a parent myself), but from my perspective, the job of the parent is assisting and protecting their child as they find their true identity as an individual. Forcing your child to act, look, or feel a certain way because of your expectations for them or because of societal expectations due to their gender can be mentally damaging.
Parents need to understand that we are living in a changing and far more accepting environment than the one they grew up in, and it's time to let our children be who they want to be.
Stop telling your boys that they "_____ like a girl."
Not only are you suggesting that girls are poor at sports and/or weak, but you're also attempting to attribute physical prowess to boys, which isn't necessarily the truth.
Think about this in terms of medals awarded at the 2016 Rio Olympics. Of the 46 gold medals won by United States individuals/teams, 27 of them went to women. Taking it a step further, women in the United States brought home 61 of 121 total medals (men brought home 55, 5 came from mixed events). If they were their own country and if you subtracted their medals earned from the total number for the United States, US women would have finished tied for the most gold medals and third most medals overall!
On what is considered one of the largest platforms (if not the largest platform) for sports in the world, US women dominated.
This isn't an insult. Stop trying to make it one. And, remember, boys don't have to be athletic to be a "man."
Girls don't have to be princesses if they don't want to be. Conversely, if your little girl wants to be a princess, let her be a princess.
If your little girl wants to roll around in the yard and get dirty and do things that are seen as primarily masculine activities, let her break the mold that was set for her when she was born a female. Barbie dolls, pink dresses and tea parties aren't for every girl. There's nothing wrong with that.
But, if your little girl wants to dress up like her favorite doll or wear a crown or waste water in plastic tea cups placed neatly in front of her favorite stuffed animals, let her be the princess she wants to be. There's nothing wrong with that either. Not every girl has to break the mold.
The moral of the story: let your daughter decide her own path. She's the one that has to be happy with her direction.
"Boys will be boys" isn't proper justification for your child's behavior.
Next time your little boy is caught doing something he shouldn't be, don't brush it off. You're doing far more damage than you may think. You're legitimizing aggression and fostering his belief that poor behavior is acceptable behavior.
Try using these moments as a chance for constructive criticism. He may not like it, and he may be upset with you; but, you need to grow thick skin and realize that hard feelings are worth teaching your child a lesson that will last far longer than his time crying in the timeout corner.
If you continue to allow your boy to act however he wants, don't complain when he embarrasses you in public because it's not his fault. You had the power and opportunity to teach him respect.
Your boy doesn't have to "man up."
There is absolutely nothing wrong with your boy being vulnerable and/or emotional. Stop making him feel bad for expressing the way he feels. Stop making him feel like he needs to be stoic to be accepted. In the twenty-first century, the model of the perfect man doesn't include the dated belief that vulnerability is synonymous with weakness.
If you're worried about other children's perception of your boy because he is sensitive, you shouldn't be. That worry is a byproduct of the world we live in--a world that deems it unacceptable for a boy to cry or feel. And, children who make fun of your boy for feeling are the byproduct of close-minded parenting.
Furthermore, not only is it okay for boys to show emotion, but it can be soothing and beneficial for developing a clean mental bill-of-health. Speaking from personal experience, allowing yourself to feel is far less damaging than suppressing emotions in order to keep up a false façade.